33921666a1
This is the Doxygen work begun in Google Summer of Code projects 2008 and 2012 and subsequently improved by numerous contributors. * vadz-doxygen: (314 commits) Add changes entry for Doxygen support Add some missing doctype tyemaps Doxygen warnings cleanup Move doxygen warning numbers Add Python doxygen example Doxygen example Add Doxygen to include paths Doxygen source rename More merge fixes from doxygen branches Correct python example headers Correct source code headers Another merge fix from doxygen branches Java enums output format fixes Add omitted doxygen_parsing_enums testcase PEP8 conformance for comment verifier module Clean up merge problem Doxygen html tweaks Update html chapter numbering for added Doxygen chapter Fixes to makechap.py to detect ill-formed headers html fixes for Doxygen Add missing CPlusPlus17.html file Format files to unix format Doxygen testcase tweak to match that in the html docs Doxygen html documentation updates and corrections Remove doxygen Examples subdirectory Beautify doxygen source code Code formatting fixes in doxygen code Remove unused doxygen code new_node refactor Various merge fixes in doxygen branches Unused variable warning fix Fix wrongly resetting indent after formulae in Doxygen comments Add support for doxygen:alias feature Get rid of meaningless return type of DoxygenParser methods Return enum, not untyped int, when classifying Doxygen commands Get rid of unnecessary "typedef enum" in C++ code Use slash, not backslash, in "C/C++" in the documentation Replace literal "<" with "<" in HTML documentation Fix broken link to java.sun.com in Doxygen documentation Fix using com.sun.tools.javadoc package under macOS Fix error reporting for special characters in Doxygen parsing code Switch Python Doxygen unit tests to use inspect.getdoc() Use correct separator in Java class path under Windows. Remove executable permission from appveyor.yml. Use JAVA_HOME value in configure to detect Java. Display JAVA_HOME value in "make java_version". Fix harmless MSVC warning in DoxygenTranslator code. Reset "_last" for all but first enum elements. Don't duplicate Javadoc from global enum Doxygen comments twice. Move Doxygen comments concatenation from the parser to the lexer. Fix shift/reduce conflicts in Doxygen pre/post comment parsing. Rewrote part of the grammar dealing with Doxygen comments for enums. No changes, just remove spurious white space only differences. Move Doxygen comment mangling from the parser to the lexer. Merge "-builtin" autodoc bugs workarounds from master into test. Quote JAVA_HOME variable value in Java test suite makefile. Remove unused C_COMMENT_STRING terminal from the grammar. Fix missing returns in the Doxygen test suite code. Fix trimming whitespace from Doxygen comments. Remove code not doing anything from PyDocConverter. Remove unused <sstream> header. Remove unreferenced struct declaration. Remove unused Swig_warn() function. Remove any whitespace before ignored Doxygen commands. Remove trailing space from one of Doxygen tests. Fix autodoc strings generated in Python builtin case and the test. Fix Doxygen unit test in Python "-builtin" case. Use class docstrings in "-builtin" Python case. Don't indent Doxygen doc strings in generated Python code. Add a possibility to flexibly ignore custom Doxygen tags. Stop completely ignoring many Doxygen comments. Fix structural Doxygen comment recognition in the parser. No changes, just make checking for Doxygen structural tags more sane. Use "//", not "#", for comments in SWIG input. Allow upper case letters and digits in Doxygen words. Pass the node the Doxygen comment is attached to to DoxygenParser. Get rid of findCommand() which duplicaed commandBelongs(). Recognize unknown Doxygen tags correctly. No real changes, just pass original command to commandBelongs(). Describe Doxygen-specific %features in a single place. Give warnings for unknown Doxygen commands in Doxygen parser. Document the return type when translating Doxygen @return to Python. Fix translated Doxygen comments for overloaded functions in Python. Also merge Doxygen comments for overloaded constructors in Python. Allow using enum elements as default values for Python functions. Don't always use "*args" for all Python wrapper functions. No real changes, just make PYTHON::check_kwargs() const. Refactor: move makeParameterName() to common Language base class. Remove long line wrapping from Python parameter list generation code. Simplify and make more efficient building Python docstrings. Translate Doxygen code blocks to Sphinx code blocks. Add a simple test of multiple parameters to Doxygen test suite. Make Python parameters types hyperlinks in the doc strings. Make Language::classLookup() and enumLookup() static. Fix arguments of @param, @return etc translations to Python. Remove unused method from PyDocConverter. No real changes, just remove an unnecessary variable. Preserve relative indentation when parsing Doxygen comments. Use Sphinx-friendly formatting for overloaded functions documentation. Add poor man trailing white space detection to Doxygen Python tests. ...
1260 lines
35 KiB
HTML
1260 lines
35 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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<html>
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<head>
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<title>SWIG and PHP</title>
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<link rel="stylesheet" type="text/css" href="style.css">
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<meta http-equiv="content-type" content="text/html; charset=UTF-8">
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</head>
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<body bgcolor="#ffffff">
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<H1><a name="Php">36 SWIG and PHP</a></H1>
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<!-- INDEX -->
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<div class="sectiontoc">
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<ul>
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<li><a href="#Php_nn1">Generating PHP Extensions</a>
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<ul>
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<li><a href="#Php_nn1_1">Building a loadable extension</a>
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<li><a href="#Php_nn1_3">Using PHP Extensions</a>
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</ul>
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<li><a href="#Php_nn2">Basic PHP interface</a>
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<ul>
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<li><a href="#Php_nn2_1">Constants</a>
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<li><a href="#Php_nn2_2">Global Variables</a>
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<li><a href="#Php_nn2_3">Functions</a>
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|
<li><a href="#Php_nn2_4">Overloading</a>
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<li><a href="#Php_nn2_5">Pointers and References</a>
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<li><a href="#Php_nn2_6">Structures and C++ classes</a>
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<ul>
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<li><a href="#Php_nn2_6_1">Using -noproxy</a>
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<li><a href="#Php_nn2_6_2">Constructors and Destructors</a>
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<li><a href="#Php_nn2_6_3">Static Member Variables</a>
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<li><a href="#Php_nn2_6_4">Static Member Functions</a>
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<li><a href="#Php_nn2_6_5">Specifying Implemented Interfaces</a>
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</ul>
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<li><a href="#Php_nn2_7">PHP Pragmas, Startup and Shutdown code</a>
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</ul>
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<li><a href="#Php_nn3">Cross language polymorphism</a>
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<ul>
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<li><a href="#Php_nn3_1">Enabling directors</a>
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<li><a href="#Php_nn3_2">Director classes</a>
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<li><a href="#Php_nn3_3">Ownership and object destruction</a>
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|
<li><a href="#Php_nn3_4">Exception unrolling</a>
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<li><a href="#Php_nn3_5">Overhead and code bloat</a>
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<li><a href="#Php_nn3_6">Typemaps</a>
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<li><a href="#Php_nn3_7">Miscellaneous</a>
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</ul>
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</ul>
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</div>
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<!-- INDEX -->
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<p>
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In this chapter, we discuss SWIG's support of PHP. SWIG currently supports
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generating wrappers for PHP7. Support for PHP5 was removed in SWIG 4.0.0
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and support for PHP4 was removed in SWIG 1.3.37.
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</p>
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<p>
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Currently any PHP7 release should work.
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</p>
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<p>
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In order to use this module, you will need to have a copy of the PHP
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include files to compile the SWIG generated files. If you installed
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PHP from a binary package, you may need to install a "php-dev" or "php-devel"
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package for these to be installed. You can find out where these files are
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by running <tt>php-config --includes</tt>. To use the built PHP module you
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will need either the php binary or the Apache php module. If you want to build
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your extension into php directly, you will need the complete PHP source tree
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available.
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</p>
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<H2><a name="Php_nn1">36.1 Generating PHP Extensions</a></H2>
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<p>
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To build a PHP extension, run swig using the <tt>-php7</tt> option as follows
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(<tt>-php</tt> is also supported and currently is an alias for <tt>-php7</tt>
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but prior to SWIG 4.0.0 it was an alias for <tt>-php5</tt>):
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</p>
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<div class="code"><pre>
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swig -php7 example.i
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</pre></div>
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<p>
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This will produce 3 files example_wrap.c, php_example.h and
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example.php. The first file, <tt>example_wrap.c</tt> contains all of
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the C code needed to build a PHP extension. The second file,
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<tt>php_example.h</tt> contains the header information needed if
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you wish to statically link the extension into the php interpreter.
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The third file,
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<tt>example.php</tt> can be included by PHP scripts. It attempts to
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dynamically load the extension and contains extra php code specified
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in the interface file. If wrapping C++ code with PHP classes, it will
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also contain PHP class wrappers.
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</p>
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<p>
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SWIG can generate PHP extensions from C++ libraries as well when
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given the <tt>-c++</tt> option. The support for C++ is discussed in
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more detail in <a href="#Php_nn2_6">section 27.2.6</a>. The generated
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C++ wrapper will be called example_wrap.cxx. You can specify a
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different extension for the C++ wrapper using <tt>-cppext</tt> -
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e.g. if you want example_wrap.cc use <tt>-cppext cc</tt>.
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</p>
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<p>
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The usual (and recommended) way is to build the extension as a separate
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dynamically loaded module (which is supported by all modern operating
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systems).
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</p>
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<p>
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It is also possible to rebuild PHP from source so that your module is
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statically linked into the php executable/library. This is a lot more
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work, and also requires a full rebuild of PHP to update your module,
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and it doesn't play nicely with package system. We don't recommend
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this approach, or provide explicit support for it.
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</p>
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<H3><a name="Php_nn1_1">36.1.1 Building a loadable extension</a></H3>
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<p>
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To build your module as a dynamically loadable extension, use compilation
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commands like these (if you aren't using GCC, the commands will be different,
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|
and there may be some variation between platforms - these commands should at
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least work for Linux though):
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</p>
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<div class="code"><pre>
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gcc `php-config --includes` -fpic -c example_wrap.c example.c
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gcc -shared example_wrap.o example.o -o example.so
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</pre></div>
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|
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<H3><a name="Php_nn1_3">36.1.2 Using PHP Extensions</a></H3>
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<p>
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To test the extension from a PHP script, you first need to tell PHP to
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load it. To do this, add a line like this to the <tt>[PHP]</tt> section of
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<tt>php.ini</tt>:
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</p>
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|
<div class="code"><pre>
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extension=/path/to/modulename.so
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</pre></div>
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<p>
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If the module is in PHP's default extension directory, you can omit the path.
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</p>
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<p>
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For some SAPIs (for example, the CLI SAPI) you can instead use the
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<a href="http://php.net/manual/en/function.dl.php">dl() function</a> to load
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an extension at run time, by adding a line like this to the start of each
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PHP script which uses your extension:
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</p>
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<div class="code"><pre>
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dl("/path/to/modulename.so"); // Load the module
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</pre></div>
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<p>
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But note that <tt>dl()</tt> isn't supported when running PHP through a
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webserver - you'll need to use <tt>extension</tt> in <tt>php.ini</tt> as
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described above.
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</p>
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<p>
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The PHP module which SWIG generates will also attempt to do the <tt>dl()</tt>
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call for you if the extension isn't already loaded:
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</p>
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<div class="code"><pre>
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include("example.php");
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</pre></div>
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<p>
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This PHP module also defines the PHP classes for the wrapped API, so you'll
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almost certainly want to include it anyway.
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</p>
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|
<H2><a name="Php_nn2">36.2 Basic PHP interface</a></H2>
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|
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<p>
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It is important to understand that PHP uses a single global namespace
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into which all symbols from extension modules are loaded. It is quite
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possible for names of symbols in one extension module to clash with
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other symbols unless care is taken to <tt>%rename</tt> them. At present
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SWIG doesn't have support for generating wrappers which make use of PHP's
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namespace feature.
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</p>
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<H3><a name="Php_nn2_1">36.2.1 Constants</a></H3>
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|
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<p>
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These work in much the same way as in C/C++. Constants can be defined
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by using either the normal C pre-processor declarations, or the
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<tt>%constant</tt> SWIG directive. These will then be available from
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your PHP script as a PHP constant, (i.e. no dollar sign is needed to
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access them.) For example, with a swig interface file like this,
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</p>
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<div class="code"><pre>
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%module example
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#define PI 3.14159
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%constant int E = 2.71828
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</pre>
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</div>
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<p>
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you can access the constants in your PHP script like this,
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</p>
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<div class="code"><pre>
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include("example.php");
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echo "PI = " . PI . "\n";
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echo "E = " . E . "\n";
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</pre>
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</div>
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<p>
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There's one peculiarity of how constants work in PHP which it is useful
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to note (this is not specific to SWIG though) - if you try to use an undeclared
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constant, PHP will emit a notice and then expand the constant to a string
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version of the constant's name. Unfortunately it is easy to miss the notice
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if you're using PHP in a webserver, as it will probably end up in error.log or
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similar.
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</p>
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<p>
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For example,
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</p>
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<div class="code"><pre>
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%module example
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#define EASY_TO_MISPELL 0
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</pre>
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</div>
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<p>
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accessed incorrectly in PHP,
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</p>
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<div class="code">
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<pre>
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include("example.php");
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if(EASY_TO_MISPEL) {
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...
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} else {
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...
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}
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</pre>
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</div>
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<p>
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The mis-spelled constant will become the string 'EASY_TO_MISPEL', which
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is treated as true by the if test, when the value of the intended constant
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would be treated as false! Modern versions of PHP will at least issue
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a PHP notice by default when this happens.
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</p>
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<H3><a name="Php_nn2_2">36.2.2 Global Variables</a></H3>
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<p>
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Because PHP does not provide a mechanism to intercept access and
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assignment of global variables, global variables are supported through
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the use of automatically generated accessor functions.
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</p>
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<div class="code"><pre>
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%module example;
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%inline %{
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double seki = 2;
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void print_seki() {
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zend_printf("seki is now %f\n", seki);
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}
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%}
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</pre></div>
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<p>
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is accessed as follows:
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</p>
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<div class="code"><pre>
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include("example.php");
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print seki_get();
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seki_set( seki_get() * 2); # The C variable is now 4.
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print seki_get();
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</pre></div>
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<p>
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SWIG supports global variables of all C datatypes including pointers
|
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and complex objects. Additional types can be supported by using the
|
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<tt>varinit</tt> typemap.
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</p>
|
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|
|
<p>
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SWIG honors the <tt>%immutable</tt> modifier by not generating code
|
|
for the <tt>_set</tt> method. This provides read-only access to the
|
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variable from the php script. Attempting to access the <tt>_set</tt>
|
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method will result in a php fatal error because the function is
|
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undefined.
|
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</p>
|
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|
|
<p>
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At this time SWIG does not support custom accessor methods.
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</p>
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|
|
<H3><a name="Php_nn2_3">36.2.3 Functions</a></H3>
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|
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<p>
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C functions are converted into PHP functions. Default/optional arguments are
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also allowed. An interface file like this :
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</p>
|
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|
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<div class="code"><pre>
|
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%module example
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int foo(int a);
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double bar(double, double b = 3.0);
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...
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</pre></div>
|
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<p>
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Will be accessed in PHP like this :
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</p>
|
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<div class="code"><pre>
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include("example.php");
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$a = foo(2);
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$b = bar(3.5, -1.5);
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$c = bar(3.5); # Use default argument for 2nd parameter
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|
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</pre></div>
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<!-- This isn't correct for 1.3.30 and needs rewriting to reflect reality
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<p>
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Because PHP is a dynamically typed language, the default typemaps
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used for simple types will attempt to coerce the arguments into the appropriate type. That is the following invocations are equivalent:
|
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</p>
|
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<div class="code"><pre>
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$a = foo(2);
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$a = foo("2");
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$a = foo(2.0);
|
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</pre></div>
|
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<p>
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Functions are invoked using pass by value semantics like all of PHP.
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This means the conversion which automatically takes place when
|
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invoking a swig wrapped method does not change the native type of the
|
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argument variable.
|
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</p>
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<div class="code"><pre>
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$s = "2 A string representing two";
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$a = foo($s); # invokes 'foo(2)';
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print $s; # The value of $s was not changed.
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</pre></div>
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-->
|
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|
|
|
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<H3><a name="Php_nn2_4">36.2.4 Overloading</a></H3>
|
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|
|
|
|
<p>
|
|
Although PHP does not support overloading functions natively, swig
|
|
will generate dispatch functions which will use <tt>%typecheck</tt>
|
|
typemaps to allow overloading. This dispatch function's operation and
|
|
precedence is described in <a
|
|
href="SWIGPlus.html#SWIGPlus_overloaded_methods">Overloaded functions and methods</a>.
|
|
</p>
|
|
|
|
<!-- This isn't correct for 1.3.30 and needs rewriting to reflect reality
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<p>
|
|
Because PHP is a dynamically typed language, simple values can be
|
|
silently converted from one type to another. For example, integers,
|
|
doubles and strings silently convert to each other depending on
|
|
context. This situation make overloading slightly problematic because
|
|
given the following function:
|
|
</p>
|
|
|
|
<div class="code"><pre>
|
|
void doit( int i );
|
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void doit( double i );
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</pre></div>
|
|
|
|
<p>
|
|
it is questionable which to invoke when <tt>doit("2");</tt> is used in
|
|
PHP. The string <tt>"2"</tt> simultaneously represents the integer
|
|
<tt>2</tt> and the double <tt>2.0</tt>.
|
|
</p>
|
|
|
|
<p>
|
|
In order to provide the most natural experience to PHP programmers,
|
|
the default <tt>%typecheck</tt> implemented in <tt>php.swg</tt>
|
|
allows any simple type (integer, double, string) in PHP to be used for
|
|
any simple C type (int, double, char *). The function selected then
|
|
depends only on the argument type precedence defined by SWIG.
|
|
</p>
|
|
|
|
<p>
|
|
It should be noted that <tt>SWIGTYPE</tt> references and pointers will
|
|
not be silently converted. So these two functions:
|
|
</p>
|
|
|
|
<div class="code"><pre>
|
|
void doit( const Vector & );
|
|
void doit( int i );
|
|
</pre></div>
|
|
|
|
<p>
|
|
Cause less confusion and <tt>doit("2");</tt> will invoke the function
|
|
taking the integer argument.
|
|
</p>
|
|
-->
|
|
|
|
<H3><a name="Php_nn2_5">36.2.5 Pointers and References</a></H3>
|
|
|
|
|
|
<p>
|
|
Pointers to C/C++ objects are represented
|
|
as PHP resources, rather like MySQL connection handles.
|
|
</p>
|
|
|
|
<p>
|
|
There are multiple ways to wrap pointers to simple types. Given the
|
|
following C method:
|
|
</p>
|
|
|
|
<div class="code"><pre>
|
|
void add( int *in1, int *in2, int *result);
|
|
</pre></div>
|
|
|
|
<p>
|
|
One can include <b>cpointer.i</b> to generate PHP wrappers to <tt>int
|
|
*</tt>.
|
|
</p>
|
|
|
|
<div class="code"><pre>
|
|
%module example
|
|
%include "cpointer.i"
|
|
%pointer_functions(int, intp)
|
|
|
|
void add( int *in1, int *in2, int *result);
|
|
</pre></div>
|
|
|
|
<p>
|
|
This will result in the following usage in PHP:
|
|
</p>
|
|
|
|
<div class="code"><pre>
|
|
<?php
|
|
|
|
include("example.php");
|
|
|
|
$in1=copy_intp(3);
|
|
$in2=copy_intp(5);
|
|
$result=new_intp();
|
|
|
|
add( $in1, $in2, $result );
|
|
|
|
echo "The sum " . intp_value($in1) . " + " . intp_value($in2) . " = " . intp_value( $result) . "\n";
|
|
?>
|
|
</pre></div>
|
|
|
|
<p>
|
|
An alternative would be to use the include <b>typemaps.i</b> which
|
|
defines named typemaps for INPUT, OUTPUT and INOUT variables. One
|
|
needs to either <tt>%apply</tt> the appropriate typemap or adjust the
|
|
parameter names as appropriate.
|
|
</p>
|
|
|
|
<div class="code"><pre>
|
|
%module example
|
|
%include "typemaps.i"
|
|
|
|
void add( int *INPUT, int *INPUT, int *OUTPUT);
|
|
|
|
</pre></div>
|
|
|
|
<p>
|
|
This will result in the following usage in PHP:
|
|
</p>
|
|
|
|
<div class="code"><pre>
|
|
<?php
|
|
|
|
include("example.php");
|
|
|
|
$in1 = 3;
|
|
$in2 = 5;
|
|
$result= add($in1, $in2); # Note using variables for the input is unnecessary.
|
|
|
|
echo "The sum $in1 + $in2 = $result\n";
|
|
?>
|
|
</pre></div>
|
|
|
|
<p>
|
|
Because PHP has a native concept of reference, it may seem more natural
|
|
to the PHP developer to use references to pass pointers. To enable
|
|
this, one needs to include <b>phppointers.i</b> which defines the
|
|
named typemap REF.
|
|
</p>
|
|
|
|
<p>
|
|
In case you write your own typemaps, SWIG supports an attribute called
|
|
<tt>byref</tt>: if you set that, then SWIG will make sure that the generated
|
|
wrapper function will want the input parameter as a reference.
|
|
</p>
|
|
|
|
<div class="code"><pre>
|
|
%module example
|
|
%include "phppointers.i"
|
|
|
|
void add( int *REF, int *REF, int *REF);
|
|
|
|
</pre></div>
|
|
|
|
<p>
|
|
This will result in the following usage in PHP:
|
|
</p>
|
|
|
|
<div class="code"><pre>
|
|
<?php
|
|
|
|
include("example.php");
|
|
|
|
$in1 = 3;
|
|
$in2 = 5;
|
|
$result = 0;
|
|
add($in1, $in2, $result);
|
|
|
|
echo "The sum $in1 + $in2 = $result\n";
|
|
?>
|
|
</pre></div>
|
|
|
|
<p>
|
|
It is important to note that a php variable which is NULL when passed
|
|
by reference would end up passing a NULL pointer into the function.
|
|
In PHP, an unassigned variable (i.e. where the first reference to the
|
|
variable is not an assignment) is
|
|
NULL. In the above example, if any of the three variables had not
|
|
been assigned, a NULL pointer would have been passed into
|
|
<tt>add</tt>. Depending on the implementation of the function, this
|
|
may or may not be a good thing.
|
|
</p>
|
|
|
|
<p>
|
|
We chose to allow passing NULL pointers into functions because that is
|
|
sometimes required in C libraries. A NULL pointer can be created in
|
|
PHP in a number of ways: by using <tt>unset</tt> on an existing
|
|
variable, or assigning <tt>NULL</tt> to a variable.
|
|
</p>
|
|
|
|
<H3><a name="Php_nn2_6">36.2.6 Structures and C++ classes</a></H3>
|
|
|
|
|
|
<p>
|
|
SWIG defaults to wrapping C++ structs and classes with PHP classes - this
|
|
is done by generating a PHP wrapper script which defines proxy classes
|
|
which calls a set of flat functions which actually wrap the C++ class.
|
|
You can disable this wrapper layer by passing the command-line option
|
|
"-noproxy" in which case you'll just get the flat functions.
|
|
</p>
|
|
|
|
<p>
|
|
This interface file
|
|
</p>
|
|
|
|
<div class="code"><pre>
|
|
%module vector
|
|
|
|
class Vector {
|
|
public:
|
|
double x, y, z;
|
|
Vector();
|
|
~Vector();
|
|
double magnitude();
|
|
};
|
|
|
|
struct Complex {
|
|
double re, im;
|
|
};
|
|
</pre></div>
|
|
|
|
<p>
|
|
Would be used in the following way from PHP:
|
|
</p>
|
|
|
|
<div class="code"><pre>
|
|
<?php
|
|
require "vector.php";
|
|
|
|
$v = new Vector();
|
|
$v->x = 3;
|
|
$v->y = 4;
|
|
$v->z = 5;
|
|
|
|
echo "Magnitude of ($v->x, $v->y, $v->z) = " . $v->magnitude() . "\n";
|
|
|
|
$v = NULL; # destructor called.
|
|
|
|
$c = new Complex();
|
|
|
|
$c->re = 0;
|
|
$c->im = 0;
|
|
|
|
# $c destructor called when $c goes out of scope.
|
|
?>
|
|
</pre></div>
|
|
|
|
<p>
|
|
Member variables and methods are accessed using the <tt>-></tt> operator.
|
|
</p>
|
|
|
|
<H4><a name="Php_nn2_6_1">36.2.6.1 Using -noproxy</a></H4>
|
|
|
|
|
|
<p>
|
|
The <tt>-noproxy</tt> option flattens the object structure and
|
|
generates collections of named functions (these are the functions
|
|
which the PHP class wrappers call). The above example results
|
|
in the following PHP functions:
|
|
</p>
|
|
|
|
<div class="code"><pre>
|
|
new_Vector();
|
|
Vector_x_set($obj, $d);
|
|
Vector_x_get($obj);
|
|
Vector_y_set($obj, $d);
|
|
Vector_y_get($obj);
|
|
Vector_z_set($obj, $d);
|
|
Vector_z_get($obj);
|
|
Vector_magnitude($obj);
|
|
new_Complex();
|
|
Complex_re_set($obj, $d);
|
|
Complex_re_get($obj);
|
|
Complex_im_set($obj, $d);
|
|
Complex_im_get($obj);
|
|
</pre></div>
|
|
|
|
<H4><a name="Php_nn2_6_2">36.2.6.2 Constructors and Destructors</a></H4>
|
|
|
|
|
|
<p>
|
|
The constructor is called when <tt>new Object()</tt> (or
|
|
<tt>new_Object()</tt> if using <tt>-noproxy</tt>) is used to create an
|
|
instance of the object. If multiple constructors are defined for an
|
|
object, function overloading will be used to determine which
|
|
constructor to execute.
|
|
</p>
|
|
|
|
<p>
|
|
Because PHP uses reference counting to manage resources, simple
|
|
assignment of one variable to another such as:
|
|
</p>
|
|
|
|
<div class="code"><pre>
|
|
$ref = $v;
|
|
</pre></div>
|
|
|
|
<p>
|
|
causes the symbol <tt>$ref</tt> to refer to the same underlying object
|
|
as <tt>$v</tt>. This does not result in a call to the C++ copy
|
|
constructor or copy assignment operator.
|
|
</p>
|
|
|
|
<p>
|
|
One can force execution of the copy constructor by using:
|
|
</p>
|
|
<div class="code"><pre>
|
|
$o_copy = new Object($o);
|
|
</pre></div>
|
|
|
|
<p>
|
|
Destructors are automatically called when all variables referencing
|
|
the instance are reassigned or go out of scope. The destructor is not
|
|
available to be called manually. To force a destructor to be called
|
|
the programmer can either reassign the variable or call
|
|
<tt>unset($v)</tt>
|
|
</p>
|
|
|
|
<H4><a name="Php_nn2_6_3">36.2.6.3 Static Member Variables</a></H4>
|
|
|
|
|
|
<p>
|
|
Static member variables in C++ are not wrapped as such in PHP
|
|
as it does not appear to be possible to intercept accesses to such variables.
|
|
Therefore, static member variables are
|
|
wrapped using a class function with the same name, which
|
|
returns the current value of the class variable. For example
|
|
</p>
|
|
|
|
<div class="code"><pre>
|
|
%module example
|
|
|
|
class Ko {
|
|
static int threats;
|
|
};
|
|
|
|
</pre></div>
|
|
|
|
<p>
|
|
would be accessed in PHP as,
|
|
</p>
|
|
|
|
<div class="code"><pre>
|
|
include("example.php");
|
|
|
|
echo "There have now been " . Ko::threats() . " threats\n";
|
|
|
|
</pre></div>
|
|
|
|
<p>
|
|
To set the static member variable, pass the value as the argument to the class
|
|
function, e.g.
|
|
</p>
|
|
|
|
<div class="code"><pre>
|
|
|
|
Ko::threats(10);
|
|
|
|
echo "There have now been " . Ko::threats() . " threats\n";
|
|
|
|
</pre></div>
|
|
<H4><a name="Php_nn2_6_4">36.2.6.4 Static Member Functions</a></H4>
|
|
|
|
|
|
<p>
|
|
Static member functions are supported in PHP using the
|
|
<tt>class::function()</tt> syntax. For example
|
|
</p>
|
|
|
|
<div class="code"><pre>
|
|
%module example
|
|
class Ko {
|
|
static void threats();
|
|
};
|
|
</pre></div>
|
|
|
|
would be executed in PHP as,
|
|
<div class="code"><pre>
|
|
include("example.php");
|
|
Ko::threats();
|
|
</pre></div>
|
|
|
|
|
|
<H4><a name="Php_nn2_6_5">36.2.6.5 Specifying Implemented Interfaces</a></H4>
|
|
|
|
|
|
<p>
|
|
PHP supports the concept of abstract interfaces which a class can implement.
|
|
Since SWIG 3.0.3, you can tell SWIG that a wrapped class (for example
|
|
<code>MyIterator</code>) implements the <code>Iterator</code> interface like
|
|
so:
|
|
</p>
|
|
|
|
<div class="code"><pre>
|
|
%typemap("phpinterfaces") MyIterator "Iterator";
|
|
</pre></div>
|
|
|
|
<p>
|
|
If there are multiple interfaces, just list them separated by commas.
|
|
</p>
|
|
|
|
<H3><a name="Php_nn2_7">36.2.7 PHP Pragmas, Startup and Shutdown code</a></H3>
|
|
|
|
|
|
<p>
|
|
To place PHP code in the generated "example.php" file one can use the
|
|
<b>code</b> pragma. The code is inserted after loading the shared
|
|
object.
|
|
</p>
|
|
|
|
<div class="code"><pre>
|
|
%module example
|
|
%pragma(php) code="
|
|
# This code is inserted into example.php
|
|
echo \"example.php execution\\n\";
|
|
"
|
|
</pre></div>
|
|
|
|
<p>
|
|
Results in the following in "example.php"
|
|
</p>
|
|
|
|
<div class="code"><pre>
|
|
# This code is inserted into example.php
|
|
echo "example.php execution\n";
|
|
</pre></div>
|
|
|
|
<p>
|
|
The <b>version</b> pragma can be used to add version to generated PHP extension module. The version is inserted in the zend_module_entry block.
|
|
</p>
|
|
|
|
<div class="code"><pre>
|
|
%module example
|
|
%pragma(php) version="1.5"
|
|
</pre></div>
|
|
|
|
<p>
|
|
The <b>include</b> pragma is a short cut to add include statements to
|
|
the example.php file.
|
|
</p>
|
|
|
|
<div class="code"><pre>
|
|
%module example
|
|
%pragma(php) code="
|
|
include \"include.php\";
|
|
"
|
|
%pragma(php) include="include.php" // equivalent.
|
|
</pre></div>
|
|
|
|
<p>
|
|
The <b>phpinfo</b> pragma inserts code in the
|
|
<tt>PHP_MINFO_FUNCTION</tt> which is called from PHP's
|
|
phpinfo() function.
|
|
</p>
|
|
|
|
<div class="code"><pre>
|
|
%module example;
|
|
%pragma(php) phpinfo="
|
|
zend_printf("An example of PHP support through SWIG\n");
|
|
php_info_print_table_start();
|
|
php_info_print_table_header(2, \"Directive\", \"Value\");
|
|
php_info_print_table_row(2, \"Example support\", \"enabled\");
|
|
php_info_print_table_end();
|
|
"
|
|
</pre></div>
|
|
|
|
<p>
|
|
To insert code into the <tt>PHP_MINIT_FUNCTION</tt>, one can use
|
|
either <tt>%init</tt> or <tt>%minit</tt>.
|
|
</p>
|
|
|
|
<div class="code"><pre>
|
|
%module example;
|
|
%init {
|
|
zend_printf("Inserted into PHP_MINIT_FUNCTION\n");
|
|
}
|
|
%minit {
|
|
zend_printf("Inserted into PHP_MINIT_FUNCTION\n");
|
|
}
|
|
</pre></div>
|
|
|
|
<p>
|
|
To insert code into the <tt>PHP_MSHUTDOWN_FUNCTION</tt>, one can use
|
|
either <tt>%shutdown</tt> or <tt>%mshutdown</tt>.
|
|
</p>
|
|
|
|
<div class="code"><pre>
|
|
%module example;
|
|
%mshutdown {
|
|
zend_printf("Inserted into PHP_MSHUTDOWN_FUNCTION\n");
|
|
}
|
|
</pre></div>
|
|
|
|
<p>
|
|
The <tt>%rinit</tt> and <tt>%rshutdown</tt> statements are very similar but insert code
|
|
into the request init (PHP_RINIT_FUNCTION) and request shutdown (PHP_RSHUTDOWN_FUNCTION) code respectively.
|
|
</p>
|
|
|
|
<H2><a name="Php_nn3">36.3 Cross language polymorphism</a></H2>
|
|
|
|
|
|
<p>
|
|
Proxy classes provide a more natural, object-oriented way to access
|
|
extension classes. As described above, each proxy instance has an
|
|
associated C++ instance, and method calls to the proxy are passed to the
|
|
C++ instance transparently via C wrapper functions.
|
|
</p>
|
|
|
|
<p>
|
|
This arrangement is asymmetric in the sense that no corresponding
|
|
mechanism exists to pass method calls down the inheritance chain from
|
|
C++ to PHP. In particular, if a C++ class has been extended in PHP
|
|
(by extending the proxy class), these extensions will not be visible
|
|
from C++ code. Virtual method calls from C++ are thus not able access
|
|
the lowest implementation in the inheritance chain.
|
|
</p>
|
|
|
|
<p>
|
|
Changes have been made to SWIG 1.3.18 to address this problem and make
|
|
the relationship between C++ classes and proxy classes more symmetric.
|
|
To achieve this goal, new classes called directors are introduced at the
|
|
bottom of the C++ inheritance chain. Support for generating PHP classes
|
|
has been added in SWIG 1.3.40. The job of the directors is to route
|
|
method calls correctly, either to C++ implementations higher in the
|
|
inheritance chain or to PHP implementations lower in the inheritance
|
|
chain. The upshot is that C++ classes can be extended in PHP and from
|
|
C++ these extensions look exactly like native C++ classes. Neither C++
|
|
code nor PHP code needs to know where a particular method is
|
|
implemented: the combination of proxy classes, director classes, and C
|
|
wrapper functions takes care of all the cross-language method routing
|
|
transparently.
|
|
</p>
|
|
|
|
<H3><a name="Php_nn3_1">36.3.1 Enabling directors</a></H3>
|
|
|
|
|
|
<p>
|
|
The director feature is disabled by default. To use directors you
|
|
must make two changes to the interface file. First, add the "directors"
|
|
option to the %module directive, like this:
|
|
</p>
|
|
|
|
<div class="code">
|
|
<pre>
|
|
%module(directors="1") modulename
|
|
</pre>
|
|
</div>
|
|
|
|
<p>
|
|
Without this option no director code will be generated. Second, you
|
|
must use the %feature("director") directive to tell SWIG which classes
|
|
and methods should get directors. The %feature directive can be applied
|
|
globally, to specific classes, and to specific methods, like this:
|
|
</p>
|
|
|
|
<div class="code">
|
|
<pre>
|
|
// generate directors for all classes that have virtual methods
|
|
%feature("director");
|
|
|
|
// generate directors for all virtual methods in class Foo
|
|
%feature("director") Foo;
|
|
</pre>
|
|
</div>
|
|
|
|
<p>
|
|
You can use the %feature("nodirector") directive to turn off
|
|
directors for specific classes or methods. So for example,
|
|
</p>
|
|
|
|
<div class="code">
|
|
<pre>
|
|
%feature("director") Foo;
|
|
%feature("nodirector") Foo::bar;
|
|
</pre>
|
|
</div>
|
|
|
|
<p>
|
|
will generate directors for all virtual methods of class Foo except
|
|
bar().
|
|
</p>
|
|
|
|
<p>
|
|
Directors can also be generated implicitly through inheritance.
|
|
In the following, class Bar will get a director class that handles
|
|
the methods one() and two() (but not three()):
|
|
</p>
|
|
|
|
<div class="code">
|
|
<pre>
|
|
%feature("director") Foo;
|
|
class Foo {
|
|
public:
|
|
Foo(int foo);
|
|
virtual void one();
|
|
virtual void two();
|
|
};
|
|
|
|
class Bar: public Foo {
|
|
public:
|
|
virtual void three();
|
|
};
|
|
</pre>
|
|
</div>
|
|
|
|
<p>
|
|
then at the PHP side you can define
|
|
</p>
|
|
|
|
<div class="targetlang">
|
|
<pre>
|
|
require("mymodule.php");
|
|
|
|
class MyFoo extends Foo {
|
|
function one() {
|
|
print "one from php\n";
|
|
}
|
|
}
|
|
</pre>
|
|
</div>
|
|
|
|
|
|
<H3><a name="Php_nn3_2">36.3.2 Director classes</a></H3>
|
|
|
|
|
|
|
|
|
|
|
|
<p>
|
|
For each class that has directors enabled, SWIG generates a new class
|
|
that derives from both the class in question and a special
|
|
<tt>Swig::Director</tt> class. These new classes, referred to as director
|
|
classes, can be loosely thought of as the C++ equivalent of the PHP
|
|
proxy classes. The director classes store a pointer to their underlying
|
|
PHP object. Indeed, this is quite similar to the "_cPtr" and "thisown"
|
|
members of the PHP proxy classes.
|
|
</p>
|
|
|
|
<p>
|
|
For simplicity let's ignore the <tt>Swig::Director</tt> class and refer to the
|
|
original C++ class as the director's base class. By default, a director
|
|
class extends all virtual methods in the inheritance chain of its base
|
|
class (see the preceding section for how to modify this behavior).
|
|
Thus all virtual method calls, whether they originate in C++ or in
|
|
PHP via proxy classes, eventually end up in at the implementation in the
|
|
director class. The job of the director methods is to route these method
|
|
calls to the appropriate place in the inheritance chain. By "appropriate
|
|
place" we mean the method that would have been called if the C++ base
|
|
class and its extensions in PHP were seamlessly integrated. That
|
|
seamless integration is exactly what the director classes provide,
|
|
transparently skipping over all the messy extension API glue that binds
|
|
the two languages together.
|
|
</p>
|
|
|
|
<p>
|
|
In reality, the "appropriate place" is one of only two possibilities:
|
|
C++ or PHP. Once this decision is made, the rest is fairly easy. If the
|
|
correct implementation is in C++, then the lowest implementation of the
|
|
method in the C++ inheritance chain is called explicitly. If the correct
|
|
implementation is in PHP, the Zend API is used to call the method of the
|
|
underlying PHP object (after which the usual virtual method resolution
|
|
in PHP automatically finds the right implementation).
|
|
</p>
|
|
|
|
<p>
|
|
Now how does the director decide which language should handle the method call?
|
|
The basic rule is to handle the method in PHP, unless there's a good
|
|
reason not to. The reason for this is simple: PHP has the most
|
|
"extended" implementation of the method. This assertion is guaranteed,
|
|
since at a minimum the PHP proxy class implements the method. If the
|
|
method in question has been extended by a class derived from the proxy
|
|
class, that extended implementation will execute exactly as it should.
|
|
If not, the proxy class will route the method call into a C wrapper
|
|
function, expecting that the method will be resolved in C++. The wrapper
|
|
will call the virtual method of the C++ instance, and since the director
|
|
extends this the call will end up right back in the director method. Now
|
|
comes the "good reason not to" part. If the director method were to blindly
|
|
call the PHP method again, it would get stuck in an infinite loop. We avoid this
|
|
situation by adding special code to the C wrapper function that tells
|
|
the director method to not do this. The C wrapper function compares the
|
|
called and the declaring class name of the given method. If these are
|
|
not the same, then the C wrapper function tells the director to resolve
|
|
the method by calling up the C++ inheritance chain, preventing an
|
|
infinite loop.
|
|
</p>
|
|
|
|
<p>
|
|
One more point needs to be made about the relationship between director
|
|
classes and proxy classes. When a proxy class instance is created in
|
|
PHP, SWIG creates an instance of the original C++ class and assigns it
|
|
to <tt>->_cPtr</tt>. This is exactly what happens without directors
|
|
and is true even if directors are enabled for the particular class in
|
|
question. When a class <i>derived</i> from a proxy class is created,
|
|
however, SWIG then creates an instance of the corresponding C++ director
|
|
class. The reason for this difference is that user-defined subclasses
|
|
may override or extend methods of the original class, so the director
|
|
class is needed to route calls to these methods correctly. For
|
|
unmodified proxy classes, all methods are ultimately implemented in C++
|
|
so there is no need for the extra overhead involved with routing the
|
|
calls through PHP.
|
|
</p>
|
|
|
|
<H3><a name="Php_nn3_3">36.3.3 Ownership and object destruction</a></H3>
|
|
|
|
|
|
<p>
|
|
Memory management issues are slightly more complicated with directors
|
|
than for proxy classes alone. PHP instances hold a pointer to the
|
|
associated C++ director object, and the director in turn holds a pointer
|
|
back to the PHP object. By default, proxy classes own their C++ director
|
|
object and take care of deleting it when they are garbage collected.
|
|
</p>
|
|
|
|
<p>
|
|
This relationship can be reversed by calling the special
|
|
<tt>->thisown</tt> property of the proxy class. After setting this
|
|
property to <tt>0</tt>, the director class no longer destroys the PHP
|
|
object. Assuming no outstanding references to the PHP object remain,
|
|
the PHP object will be destroyed at the same time. This is a good thing,
|
|
since directors and proxies refer to each other and so must be created
|
|
and destroyed together. Destroying one without destroying the other will
|
|
likely cause your program to segfault.
|
|
</p>
|
|
|
|
<p>
|
|
Here is an example:
|
|
</p>
|
|
|
|
<div class="code">
|
|
<pre>
|
|
class Foo {
|
|
public:
|
|
...
|
|
};
|
|
class FooContainer {
|
|
public:
|
|
void addFoo(Foo *);
|
|
...
|
|
};
|
|
</pre>
|
|
</div>
|
|
|
|
<br>
|
|
|
|
<div class="targetlang">
|
|
<pre>
|
|
$c = new FooContainer();
|
|
$a = new Foo();
|
|
$a->thisown = 0;
|
|
$c->addFoo($a);
|
|
</pre>
|
|
</div>
|
|
|
|
<p>
|
|
In this example, we are assuming that FooContainer will take care of
|
|
deleting all the Foo pointers it contains at some point.
|
|
</p>
|
|
|
|
<H3><a name="Php_nn3_4">36.3.4 Exception unrolling</a></H3>
|
|
|
|
|
|
<p>
|
|
With directors routing method calls to PHP, and proxies routing them
|
|
to C++, the handling of exceptions is an important concern. By default, an
|
|
exception thrown in PHP code called from C++ causes the PHP interpreter
|
|
to flag that an exception is thrown, then return passes to C++ as if
|
|
the PHP function had returned <code>Null</code>. Assuming the directorout
|
|
typemaps handle this (those SWIG defines by default should) then once
|
|
control returns to PHP code again, the PHP exception will actually propagate.
|
|
</p>
|
|
|
|
<p>
|
|
Sometimes this control flow is problematic, and you want to skip any
|
|
handling in the C++ code. To achieve this, it is necessary
|
|
to temporarily translate the PHP exception into a C++ exception. This can be
|
|
achieved using the %feature("director:except") directive. The following code
|
|
should suffice in most cases:
|
|
</p>
|
|
|
|
<div class="code">
|
|
<pre>
|
|
%feature("director:except") {
|
|
if ($error == FAILURE) {
|
|
throw Swig::DirectorMethodException();
|
|
}
|
|
}
|
|
</pre>
|
|
</div>
|
|
|
|
<p>
|
|
This code will check the PHP error state after each method call from a
|
|
director into PHP, and throw a C++ exception if an error occurred. This
|
|
exception can be caught in C++ to implement an error handler.
|
|
Currently no information about the PHP error is stored in the
|
|
Swig::DirectorMethodException object, but this will likely change in the
|
|
future.
|
|
</p>
|
|
|
|
<p>
|
|
It may be the case that a method call originates in PHP, travels up to
|
|
C++ through a proxy class, and then back into PHP via a director method.
|
|
If an exception occurs in PHP at this point, it would be nice for that
|
|
exception to find its way back to the original caller. This can be done
|
|
by combining a normal %exception directive with the
|
|
<tt>director:except</tt> handler shown above. Here is an example of a
|
|
suitable exception handler:
|
|
</p>
|
|
|
|
<div class="code">
|
|
<pre>
|
|
%exception {
|
|
try { $action }
|
|
catch (Swig::DirectorException &e) { SWIG_fail; }
|
|
}
|
|
</pre>
|
|
</div>
|
|
|
|
<p>
|
|
The class Swig::DirectorException used in this example is actually a
|
|
base class of Swig::DirectorMethodException, so it will trap this
|
|
exception. Because the PHP error state is still set when
|
|
Swig::DirectorMethodException is thrown, PHP will register the exception
|
|
as soon as the C wrapper function returns.
|
|
</p>
|
|
|
|
<H3><a name="Php_nn3_5">36.3.5 Overhead and code bloat</a></H3>
|
|
|
|
|
|
<p>
|
|
Enabling directors for a class will generate a new director method for
|
|
every virtual method in the class' inheritance chain. This alone can
|
|
generate a lot of code bloat for large hierarchies. Method arguments
|
|
that require complex conversions to and from target language types can
|
|
result in large director methods. For this reason it is recommended that
|
|
you selectively enable directors only for specific classes that are
|
|
likely to be extended in PHP and used in C++.
|
|
</p>
|
|
|
|
<p>
|
|
Compared to classes that do not use directors, the call routing in the
|
|
director methods does add some overhead. In particular, at least one
|
|
dynamic cast and one extra function call occurs per method call from
|
|
PHP. Relative to the speed of PHP execution this is probably completely
|
|
negligible. For worst case routing, a method call that ultimately
|
|
resolves in C++ may take one extra detour through PHP in order to ensure
|
|
that the method does not have an extended PHP implementation. This could
|
|
result in a noticeable overhead in some cases.
|
|
</p>
|
|
|
|
<p>
|
|
Although directors make it natural to mix native C++ objects with PHP
|
|
objects (as director objects) via a common base class pointer, one
|
|
should be aware of the obvious fact that method calls to PHP objects
|
|
will be much slower than calls to C++ objects. This situation can be
|
|
optimized by selectively enabling director methods (using the %feature
|
|
directive) for only those methods that are likely to be extended in PHP.
|
|
</p>
|
|
|
|
<H3><a name="Php_nn3_6">36.3.6 Typemaps</a></H3>
|
|
|
|
|
|
<p>
|
|
Typemaps for input and output of most of the basic types from director
|
|
classes have been written. These are roughly the reverse of the usual
|
|
input and output typemaps used by the wrapper code. The typemap
|
|
operation names are 'directorin', 'directorout', and 'directorargout'.
|
|
The director code does not currently use any of the other kinds of
|
|
typemaps. It is not clear at this point which kinds are appropriate and
|
|
need to be supported.
|
|
</p>
|
|
|
|
|
|
<H3><a name="Php_nn3_7">36.3.7 Miscellaneous</a></H3>
|
|
|
|
|
|
<p> Director typemaps for STL classes are mostly in place, and hence you
|
|
should be able to use std::string, etc., as you would any other type.
|
|
</p>
|
|
|
|
</body>
|
|
</html>
|