work on #71428

Author: krakjoe

Zend/tests/bug71428.1.phpt

@@ -0,0 +1,13 @@
+--TEST--
+bug #71428.1: inheritance with null default values
+--FILE--
+<?php
+class A {
+    public function m(array $a = null) {}
+}
+class B extends A {
+    public function m(array $a = []) {}
+}
+--EXPECTF--
+Warning: Declaration of B::m(array $a = Array) should be compatible with A::m(array $a = NULL) in %sbug71428.1.php on line 7
+

Zend/zend_inheritance.c

@@ -238,6 +238,11 @@ static int zend_do_perform_type_hint_check(const zend_function *fe, zend_arg_inf
 		zend_string_release(fe_class_name);
 	}
 
+	if (proto_arg_info->allow_null && !fe_arg_info->allow_null) {
+		/* incompatible nullability */
+		return 0;
+	}
+
 	if (fe_arg_info->type_hint != proto_arg_info->type_hint) {
 		/* Incompatible type */
 		return 0;