PHP速记三元运算符“?:"解析错误意外的“:" [英] PHP Shorthand ternary operator "?:" Parse error unexpected ":"

问题描述

我刚刚将一些旧的PHP文件上传到了新服务器，并且在速记三元操作上遇到了解析错误(意外的':').例如:

$y = $x ?: "Some default";

php版本是5.2.16，这些代码简写为这些速记?:，所以在更改所有代码之前，我想我会看看是否有人对此有所了解，因为我已经有一段时间没有使用PHP了.

解决方案

仅从PHP 5.3起可用

_{表达式(expr1)吗? (expr2):(expr3)如果expr1评估为 TRUE ，则为expr2；如果expr1评估为 FALSE ，则为expr3.}

自PHP 5.3起，可以省略三元运算符的中间部分.如果expr1评估为 TRUE ，则表达式 expr1?:expr3 返回expr1，否则返回expr3. ^{此示例. /p>}

或更有用但在注释中请注意: http://www.php.net/manual/zh/control -structures.if.php#102060

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¹ _{http://php .net/manual/en/language.operators.comparison.php}

I've just uploaded some old PHP files to a new server and am getting parse errors (Unexpected ':') on shorthand ternary ops. eg:

$y = $x ?: "Some default";

php version is 5.2.16 The code is littered with these shorthand ?:, so before changing them all I thought I'd see if anyone knows anything about this as I've not used PHP for a while now.

解决方案

This is only available since PHP 5.3

_{The expression (expr1) ? (expr2) : (expr3) evaluates to expr2 if expr1 evaluates to TRUE, and expr3 if expr1 evaluates to FALSE.}

Since PHP 5.3, it is possible to leave out the middle part of the ternary operator. Expression expr1 ?: expr3 returns expr1 if expr1 evaluates to TRUE, and expr3 otherwise.¹

See this example for more context.

or a more useful but note in the comments: http://www.php.net/manual/en/control-structures.if.php#102060

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¹_{http://php.net/manual/en/language.operators.comparison.php}

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