[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/test-suite/php5/director_nested_runme.php

@@ -0,0 +1,74 @@
+<?php
+
+require "tests.php";
+require "director_nested.php";
+
+// No new functions
+check::functions(array(foo_int_advance,foo_int_do_advance,bar_step,bar_do_advance,bar_do_step,foobar_int_get_value,foobar_int_get_name,foobar_int_name,foobar_int_get_self,foobar_int_do_advance,foobar_int_do_step));
+// No new classes
+check::classes(array(Foo_int,Bar,FooBar_int));
+// now new vars
+check::globals(array());
+
+class A extends FooBar_int {
+  function do_step() {
+    return "A::do_step;";
+  }
+
+  function get_value() {
+    return "A::get_value";
+  }
+}
+
+$a = new A();
+check::equal($a->step(), "Bar::step;Foo::advance;Bar::do_advance;A::do_step;", "Bad A virtual resolution");
+
+class B extends FooBar_int {
+  function do_advance() {
+    return "B::do_advance;" . $this->do_step();
+  }
+
+  function do_step() {
+    return "B::do_step;";
+  }
+
+  function get_value() {
+    return 1;
+  }
+}
+
+$b = new B();
+
+check::equal($b->step(), "Bar::step;Foo::advance;B::do_advance;B::do_step;", "Bad B virtual resolution");
+
+class C extends FooBar_int {
+  function do_advance() {
+    return "C::do_advance;" . parent::do_advance();
+  }
+
+  function do_step() {
+    return "C::do_step;";
+  }
+
+  function get_value() {
+    return 2;
+  }
+
+  function get_name() {
+    return parent::get_name() . " hello";
+  }
+}
+
+$cc = new C();
+# TODO: Currently we do not track the dynamic type of returned 
+# objects, so we skip the get_self() call.
+#$c = Foobar_int::get_self($cc);
+$c = $cc;
+$c->advance();
+
+check::equal($c->get_name(), "FooBar::get_name hello", "get_name failed");
+
+check::equal($c->name(), "FooBar::get_name hello", "name failed");
+
+check::done();
+?>