php-问号冒号运算符的含义 [英] php - Meaning of question mark colon operator

问题描述

此行中的?:是什么意思?

$_COOKIE['user'] ?: getusername($_COOKIE['user']);

谢谢.

推荐答案

这是if语句的简写.

$username = $_COOKIE['user'] ?: getusername($_COOKIE['user']);

与

if( $_COOKIE['user'] ) 
{
    $username = $_COOKIE['user'];
} 
else
{
    $username = getusername($_COOKIE['user']); 
}

在此处查看测试套件: https://3v4l.org/6XMc4

see test suite here: https://3v4l.org/6XMc4

但是在此示例中，函数'getusername'可能无法正常工作，因为仅当$_COOKIE['user']为empty时，该函数才会击中else.因此，getusername()中的参数也为空.

But in this example, the function 'getusername' probably doesn't work correct, because it hits the else only when $_COOKIE['user'] is empty. So, the parameter inside getusername() is also kind of empty.

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