php PHP问号
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PHP question mark
提问by user829814
$hideCode = $likesObj->isAlreadyLikedByUser(facebookUID()) ? 'style="display:none;"' : '';
Can anyone explain to me what that question mark does in this line of code? Thanks a lot!
谁能向我解释这个问号在这行代码中的作用？非常感谢！
回答by nickf
This is called the Ternary Operator, and it's common to several languages, including PHP, Javascript, Python, Ruby...
这称为三元运算符，它在多种语言中都很常见，包括 PHP、Javascript、Python、Ruby...
$x = $condition ? $trueVal : $falseVal;
// same as:
if ($condition) {
$x = $trueVal;
} else {
$x = $falseVal;
}
One very important point to note, when using a ternary in PHP is this:
需要注意的一个非常重要的点，在 PHP 中使用三元时是这样的：
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
注意：请注意，三元运算符是一个语句，它的计算结果不是变量，而是语句的结果。了解是否要通过引用返回变量很重要。语句返回 $var == 42 ? $a : $b; 因此，在按引用返回的函数中将不起作用，并且在更高的 PHP 版本中会发出警告。 来源
回答by Ovais Khatri
Actually this statment is representing a Ternary operation, a conditional expression:
实际上这个语句代表一个三元运算，一个条件表达式：
// works like: (condition) ? if-true : if-false;
$hideCode = $likesObj->isAlreadyLikedByUser(facebookUID()) ? 'style="display:none;"':'';
in your case $hideCodewill have style="display:none;"value if
在你的情况下$hideCode将style="display:none;"有价值，如果
$likesObj->isAlreadyLikedByUser(facebookUID())
will return true, else it will be null or empty.
将返回 true，否则它将为 null 或为空。
回答by Patrick Desjardins
It's a shorter version of a IF statement.
它是 IF 语句的较短版本。
$hideCode = $likesObj->isAlreadyLikedByUser(facebookUID()) ? ' style="display:none;"':'';
if in fact :
如果事实上：
if($likesObj->isAlreadyLikedByUser(facebookUID()))
{
$hideCode = 'style="display:none"';
}
else
{
$hideCode = "";
}
For the purism :
对于纯粹主义：
It's representing a Ternary operation
它代表一个三元操作
回答by Aleks G
This is the simple if-then-else type logic:
这是简单的 if-then-else 类型逻辑：
(condition) ? (if-true-value) : (if-false-value)
so in your case, the condition is checked (i.e. has the page already been liked by the user); if yes (true condition), then style="display:none;"is printed so that whatever the element you're using is not displayed. Otherwise, an empty string is printed, which is the equivalent of not printing anything at all, naturally.
所以在你的情况下，条件被检查（即页面已经被用户喜欢）；如果是（真条件），则style="display:none;"打印，以便不显示您使用的任何元素。否则，打印一个空字符串，这相当于根本不打印任何东西，自然。
回答by robamaton
It's part of a ternary operator. The first part is the conditional of an if-else statement. After the question mark is the "if" block, and after the colon is the "else" block.
它是三元运算符的一部分。第一部分是 if-else 语句的条件。问号后面是“if”块，冒号后面是“else”块。
回答by Nicola Peluchetti
It is the ternary operator: it means
它是三元运算符：这意味着
if $likesObj->isAlreadyLikedByUser(facebookUID())is true assign style="display:none;to the variable, otherwise assign ''
如果$likesObj->isAlreadyLikedByUser(facebookUID())为真赋值 style="display:none;给变量，否则赋值''
回答by Webberman
$hideCode = $likesObj->isAlreadyLikedByUser(facebookUID()) ? 'style="display:none;"':'';
$hideCode = $likesObj->isAlreadyLikedByUser(facebookUID()) ？'style="display:none;"':'';
This is the same as the following:
这与以下内容相同：
if ($likesObj->isAlreadyLikedByUser(facebookUID()))
{
$hideCode = 'style="display:none;"';
}
else
{
$hideCode = '';
}
回答by Zeta Two
This is a very compact if-clause.
这是一个非常紧凑的 if 子句。
(condition) ? :
（健康）状况） ？：
