PHP: Check if string is valid regular expression

check_regex.php

<?php

function isRegularExpression($string) {
    set_error_handler(function() {}, E_WARNING);
    $isRegularExpression = preg_match($string, "") !== FALSE;
    restore_error_handler();
    return isRegularExpression;
}

This could actually be a one-liner if you don't mind using @ symbols 👍

<?php
function isRegularExpression($string) {
    return @preg_match($string, '') !== FALSE;
}
?>

This could actually be a one-liner if you don't mind using @ symbols +1

Except that @ can sometimes be disabled (with xdebug or scream extension).