`restore_xxx_handler()` does silently return even if there is no handler to restore

Description

The following code:

repro: https://3v4l.org/DDulh

<?php

restore_error_handler();
restore_error_handler();
restore_error_handler();

restore_exception_handler();
restore_exception_handler();
restore_exception_handler();

Resulted in this output:

But I expected this output instead:

php warning for each restore_xxx_handler() call if there is no handler to restore

The warnings are important to be inform the developer the operation is probably not wanted (ie. handler was never added).

PHP Version

any

Operating System

any

首先在 PHP 源代码中找到 restore_error_handler() 和 restore_exception_handler() 的实现，然后检查当前如何处理重复调用。重现所报告的调用序列，并为在没有可恢复的 handler 时进行的调用添加覆盖。完成的标准是每次此类调用都会发出预期的 PHP 警告，同时不会破坏正常的 handler 恢复。