[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

Lib/php5/const.i

@@ -0,0 +1,51 @@
+/* -----------------------------------------------------------------------------
+ * const.i
+ *
+ * Typemaps for constants
+ * ----------------------------------------------------------------------------- */
+
+%typemap(consttab) int,
+                   unsigned int,
+                   short,
+                   unsigned short,
+                   long,
+                   unsigned long,
+                   unsigned char,
+                   signed char,
+                   bool,
+                   enum SWIGTYPE
+  "SWIG_LONG_CONSTANT($symname, ($1_type)$value);";
+
+%typemap(consttab) float,
+                   double
+  "SWIG_DOUBLE_CONSTANT($symname, $value);";
+
+%typemap(consttab) char
+  "SWIG_CHAR_CONSTANT($symname, $value);";
+
+%typemap(consttab) char *,
+                   const char *,
+                   char [],
+                   const char []
+  "SWIG_STRING_CONSTANT($symname, $value);";
+
+%typemap(consttab) SWIGTYPE *,
+                   SWIGTYPE &,
+                   SWIGTYPE &&,
+                   SWIGTYPE [] {
+  zval *z_var;
+  zend_constant c;
+  size_t len = sizeof("$symname") - 1;
+  MAKE_STD_ZVAL(z_var);
+  SWIG_SetPointerZval(z_var, (void*)$value, $1_descriptor, 0);
+  c.value = *z_var;
+  zval_copy_ctor(&c.value);
+  c.name = zend_strndup("$symname", len);
+  c.name_len = len+1;
+  c.flags = CONST_CS | CONST_PERSISTENT;
+  c.module_number = module_number;
+  zend_register_constant( &c TSRMLS_CC );
+}
+
+/* Handled as a global variable. */
+%typemap(consttab) SWIGTYPE (CLASS::*) "";