Default

default is a PHP keyword, used with switch() and match() structures. It represents any case that was not already considered.

<?php

switch ($i) {
    case 0:
        echo 'i equals 0';
        break;
    case 1:
        echo 'i equals 1';
        break;
    default:
        echo 'i is not 0 nor 1';
        break;
}

?>

Documentation

Related : Switch, Match, Case, Default Value, Switch Case, Switch Default