[PHP] Add support for PHP7.

PHP5's C extension API has changed substantially so you need to use
-php7 to specify you want PHP7 compatible wrappers.
Fixes https://github.com/swig/swig/issues/571

Examples/php5/enum/runme.php

@@ -0,0 +1,32 @@
+<?php
+
+require "example.php";
+
+# ----- Object creation -----
+
+# Print out the value of some enums
+print "*** color ***";
+print "    RED    =" . RED;
+print "    BLUE   =" . BLUE;
+print "    GREEN  =" . GREEN;
+
+print "\n*** Foo::speed ***";
+print "    Foo_IMPULSE   =" . Foo_IMPULSE;
+print "    Foo_WARP      =" . Foo_WARP;
+print "    Foo_LUDICROUS =" . Foo_LUDICROUS;
+
+print "\nTesting use of enums with functions\n";
+
+enum_test(RED, Foo_IMPULSE);
+enum_test(BLUE, Foo_WARP);
+enum_test(GREEN, Foo_LUDICROUS);
+enum_test(1234,5678);
+
+print "\nTesting use of enum with class method\n";
+$f = new_Foo();
+
+Foo_enum_test($f,Foo_IMPULSE);
+Foo_enum_test($f,Foo_WARP);
+Foo_enum_test($f,Foo_LUDICROUS);
+
+?>