php - register_shutdown_function 覆盖

Question

是否可以覆盖已经设置的 register_shutdown_function 堆栈？像这样的东西:

function f1(){
    echo "f1";
}
function f2(){
    echo "f2";
}
register_shutdown_function("f1");
echo "actions here";
register_shutdown_function("f2");
call_to_undefined_function(); // to "produce" the error

在这种情况下，我希望脚本只调用 f2()。这可能吗？

Answer 1

你不能直接做，但总有一个解决方法:

$first = register_cancellable_shutdown_function(function () {
    echo "This function is never called\n";
});

$second = register_cancellable_shutdown_function(function () {
    echo "This function is going to be called\n";
});

cancel_shutdown_function($first);

输出:

$ php test.php
This function is going to be called

The code :

function register_cancellable_shutdown_function($callback)
{
        return new cancellable_shutdown_function_envelope($callback);
}

function cancel_shutdown_function($envelope)
{
    $envelope->cancel();
}

final class cancellable_shutdown_function_envelope
{
        private $callback;

        public function __construct($callback)
        {
                $this->callback = $callback;
                register_shutdown_function(function () {
                        $this->callback && call_user_func($this->callback);
                });
        }

        public function cancel()
        {
                $this->callback = false;
        }
}