Question

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What are the PHP operators “?” and “:” called and what do they do?

From http://twitto.org/

<?PHP
    require __DIR__.'/c.php';
    if (!is_callable($c = @$_GET['c'] ?: function() { echo 'Woah!'; }))
        throw new Exception('Error');
    $c();
?>

Twitto uses several new features available as of PHP 5.3:

1. The DIR constant
2. The ?: operator
3. Anonymous functions

---

1. What does number 2 do with the ?: in PHP 5.3?

2. Also, what do they mean by anonymous functions? Wasn’t that something that has existed for a while?

Answer 1

?: is a form of the conditional operator which was previously available only as:

expr ? val_if_true : val_if_false

In 5.3 it’s possible to leave out the middle part, e.g. expr ?: val_if_false which is equivalent to:

expr ? expr : val_if_false

From the manual:

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