[PHP] Don't generate code referencing undefined $r

This could happen in overloaded methods which returned void and took at
least one const std::string& parameter.

CHANGES.current

@@ -7,6 +7,11 @@ the issue number to the end of the URL: https://github.com/swig/swig/issues/
 Version 4.0.0 (in progress)
 ===========================
 
+2019-02-08: olly
+	    [PHP] Don't generate code which references $r when $r hasn't been
+	    defined.  This could happen in overloaded methods which returned
+	    void and took at least one const std::string& parameter.
+
 2019-02-08: olly
 	    [PHP] The generated code is now compatible with PHP 7.3, and the
 	    testsuite now runs cleanly with this version too.

Examples/test-suite/li_std_string.i

@@ -22,6 +22,12 @@ const std::string& test_const_reference(const std::string &x) {
    return x;
 }
 
+void test_const_reference_returning_void(const std::string &) {
+}
+
+void test_const_reference_returning_void(const std::string &, int) {
+}
+
 void test_pointer(std::string *x) {
 }
 

Examples/test-suite/php/li_std_string_runme.php

@@ -3,6 +3,17 @@
 require "tests.php";
 require "li_std_string.php";
 
+function die_on_error($errno, $errstr, $file, $line) {
+    if ($file !== Null) {
+        print $file;
+        if ($line !== Null) print ":$line";
+        print ": ";
+    }
+    print "$errstr\n";
+    exit(1);
+}
+set_error_handler("die_on_error", -1);
+
 // Global variables
 //$s="initial string";
 //check::equal(GlobalString2_get() ,"global string 2", "GlobalString2 test 1");
@@ -27,5 +38,8 @@ check::equal(Structure::StaticMemberString2(), $s, "StaticMemberString2 test 2")
 // below broken ?
 //check::equal(Structure::ConstStaticMemberString(), "const static member string", "ConstStaticMemberString test");
 
+// This used to give "Undefined variable: r"
+li_std_string::test_const_reference_returning_void("foo");
+
 check::done();
 ?>

Source/Modules/php.cxx

@@ -979,7 +979,7 @@ public:
     /* Insert argument output code */
     bool hasargout = false;
     for (i = 0, p = l; p; i++) {
-      if ((tm = Getattr(p, "tmap:argout"))) {
+      if ((tm = Getattr(p, "tmap:argout")) && Len(tm)) {
 	hasargout = true;
 	Replaceall(tm, "$source", Getattr(p, "lname"));
 	//      Replaceall(tm,"$input",Getattr(p,"lname"));