[PHP-DOC] Example for preg_last_error() function

[Felipe Pena]

if (!preg_match('/(?:\D+|<\d+>)*[!?]/', 'abcdefghihklmno')) {
    switch (preg_last_error()) {
        case PREG_BACKTRACK_LIMIT_ERROR:
            print "Backtrack limit exhausted!\n";
            break;
    }
}