filter unused code

src/operators.cc

@@ -247,6 +247,7 @@ namespace php_arma
         });
     }
 
+#if PHP_VERSION_ID >= 70400
     int assign_op_handler(zend_execute_data *execute_data)
     {
         switch (EX(opline)->extended_value) {
@@ -266,6 +267,7 @@ namespace php_arma
                 return ZEND_USER_OPCODE_DISPATCH;
         }
     }
+#endif
 
     template <typename... Ts>
     zend_always_inline