[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/value/runme.php

@@ -0,0 +1,43 @@
+<?php
+
+	require "example.php";
+
+
+	$v = new_vector();
+        vector_x_set($v,1.0);
+        vector_y_set($v,2.0);
+        vector_z_set($v,3.0);
+
+	$w = new_vector();
+        vector_x_set($w,10.0);
+        vector_y_set($w,11.0);
+        vector_z_set($w,12.0);
+
+	echo "I just created the following vector\n";
+	vector_print($v);
+	vector_print($w);
+
+	echo "\nNow I'm going to compute the dot product\n";
+
+	$d = dot_product($v, $w);
+
+	echo "dot product = $d (should be 68)\n";
+
+	echo "\nNow I'm going to add the vectors together\n";
+
+        $r = new_vector();
+	vector_add($v, $w, $r);
+
+	vector_print($r);
+
+	echo "The value should be (11,13,15)\n";
+
+	echo "\nNow I'm going to clean up the return result\n";
+
+#	free($r);
+
+	echo "Good\n";
+
+?>
+
+