standard: Use specialised macro in array_merge()

Author: ndossche

ext/standard/array.c

@@ -4311,7 +4311,7 @@ static zend_always_inline void php_array_merge_wrapper(INTERNAL_FUNCTION_PARAMET
 				bool copy = 1;
 				zend_string *string_key;
 
-				ZEND_HASH_FOREACH_STR_KEY(Z_ARRVAL_P(ret), string_key) {
+				ZEND_HASH_MAP_FOREACH_STR_KEY(Z_ARRVAL_P(ret), string_key) {
 					if (!string_key) {
 						copy = 0;
 						break;