PHP Shorthand ternary operator “?:” Parse error unexpected “:”

问题

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.

回答1:

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}

回答2:

Since you are using php 5.2.16, your ternary requires 2 options e.g

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

Variable = condition ? true value : false value ;

来源：https://stackoverflow.com/questions/6277222/php-shorthand-ternary-operator-parse-error-unexpected