Adding correct check and error message

Author: CViniciusSDias

ext/standard/string.c

@@ -1033,9 +1033,14 @@ PHP_FUNCTION(implode)
 		Z_PARAM_ARRAY_HT_OR_NULL(pieces)
 	ZEND_PARSE_PARAMETERS_END();
 
+	if (arg1_str != NULL && pieces == NULL) {
+		zend_type_error("%s(): Argument #2 ($array) must be of type array, null given", get_active_function_name());
+		RETURN_THROWS();
+	}
+
 	if (pieces == NULL) {
 		if (arg1_array == NULL) {
-			zend_type_error("%s(): Argument #1 ($array) must be of type array, null given", get_active_function_name());
+			zend_type_error("%s(): Argument #1 ($array) must be of type array, string given", get_active_function_name());
 			RETURN_THROWS();
 		}