PHP问号 [英] PHP question mark

问题描述

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

有人可以在这行代码中向我解释那个问号是做什么的吗?非常感谢！

Can anyone explain to me what that question mark does in this line of code? Thanks a lot!

推荐答案

这称为三元运算符，这是多种语言的通用语言，包括PHP，Javascript，Python，Ruby ...

This is called the Ternary Operator, and it's common to several languages, including PHP, Javascript, Python, Ruby...

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

// same as:

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

在PHP中使用三进制时，需要注意的一个非常重要的一点是:

One very important point to note, when using a ternary in PHP is this:

注意:请注意，三元运算符是一个语句，它的结果不是变量，而是变量的结果.要知道是否要通过引用返回变量，这一点很重要.语句返回$ var == 42? $ a:$ b;因此，按引用返回功能中的无效将起作用，并且在更高版本的PHP中会发出警告. _源

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

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