[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/class/runme.php

@@ -0,0 +1,60 @@
+<?php
+
+# This example illustrates how member variables are wrapped.
+
+require("example.php");
+
+# ----- Object creation -----
+
+print "Creating some objects:\n";
+$c = new Circle(10);
+print "    Created circle\n";
+$s = new Square(10);
+print "    Created square\n";
+
+# ----- Access a static member -----
+
+print "\nA total of " . Shape::nshapes() . " shapes were created\n";
+
+# ----- Member data access -----
+
+# Set the location of the object.
+# Note: methods in the base class Shape are used since
+# x and y are defined there.
+
+$c->x = 20;
+$c->y = 30;
+$s->x = -10;
+$s->y = 5;
+
+print "\nHere is their current position:\n";
+print "    Circle = ({$c->x},{$c->y})\n";
+print "    Square = ({$s->x},{$s->y})\n";
+
+# ----- Call some methods -----
+
+# Notice how the Shape_area() and Shape_perimeter() functions really
+# invoke the appropriate virtual method on each object.
+print "\nHere are some properties of the shapes:\n";
+foreach (array($c,$s) as $o) {
+      print "    ". get_class($o) . "\n";
+      print "        area      = {$o->area()}\n";
+      print "        perimeter = {$o->perimeter()}\n";
+}
+
+# ----- Delete everything -----
+
+print "\nGuess I'll clean up now\n";
+
+# Note: this invokes the virtual destructor
+$c = NULL;
+$s = NULL;
+
+# and don't forget the $o from the for loop above.  It still refers to
+# the square.
+$o = NULL;
+
+print Shape::nshapes() . " shapes remain\n";
+print "Goodbye\n";
+
+?>