Short Ternary Operator

The expression (expr1) ?: (expr3) evaluates to expr2 if expr1 evaluates to empty(), and expr3 if expr1 evaluates to false.

Is is a short version of the ternary operator, and it is often used to set default values in a concise way.

<?php

$action = (empty($_POST['action'])) ? 'default';

?>

Documentation

See also Short Hand Comparison in PHP

Related : Ternary Operator, Coalesce Operator

Added in PHP 5.3+