The ?: Operator in PHP 5.3

PHP 5.3 introduced the ?: operator, a condensed form of the conditional operator that was previously available. Originally, the conditional operator took the form:

expr ? val_if_true : val_if_false

In PHP 5.3, you can omit the middle part, leading to the ?: syntax. This is equivalent to:

expr ? expr : val_if_false

For example, the following code checks if the variable $c is callable. If it isn't, it throws an exception:

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

Anonymous Functions in PHP 5.3

Along with the ?: operator, PHP 5.3 also introduced anonymous functions. Contrary to the question, anonymous functions have not existed for a while. They were a new feature in PHP 5.3. Anonymous functions are created without a name and are typically used as callbacks or as arguments to other functions.

In the example above, the anonymous function is assigned to the variable $c. It has no parameters and prints "Woah!" when called. This anonymous function is used as a default value for the $c variable, which checks if the function is callable before attempting to execute it.