PHP问号

Question

$hideCode = $likesObj->isAlreadyLikedByUser(facebookUID()) ? 'style="display:none;"' : '';

任何人都可以向我解释一下这行代码中问号的作用吗？非常感谢!

Answer 1

这被称为 Ternary Operator ，并且它对多种语言都很常见，包括 PHP、Javascript、Python、Ruby...

$x = $condition ? $trueVal : $falseVal;

// same as:

if ($condition) {
    $x = $trueVal;
} else {
    $x = $falseVal;
}

在 PHP 中使用三元组时需要注意的一点是:

Note: Please note that the ternary operator is a statement, and that it doesn't evaluate to a variable, but to the result of a statement. This is important to know if you want to return a variable by reference. The statement return $var == 42 ? $a : $b; in a return-by-reference function will therefore not work and a warning is issued in later PHP versions. _source