php7 php_str_to_str warning: assignment makes pointer from integer without a cast

Hello prehistory: i tried to use php_str_to_str function to replace some character insteed of use call_user_func with str_replace  in ext/standard/string.c  PHPAPI zend_string *php_str_to_str(char *haystack, size_t length, char *needle, size_t needle_len, char *str, size_t str_len); so i expect a zend_string as result ? but when i build i got a warning: assignment makes pointer from integer without a cast  buf = php_str_to_str(value,strlen(value),"y",1,"J",1);     ^ buf is: zend_string *buf; When buf is: int buf; i got no warning. i found 2 examples which looks like i have done  ext/standard/var.c win32/sendmail.c Best Regards Torsten