Allow user to compute maths in PHP

maths.php

<?php

function mathEval($q)
{
    $q = preg_replace('/\s+/', '', $q);

    $number = '(?:\d+(?:[,.]\d+)?|pi|π)';
    $functions = '(?:sinh?|cosh?|tanh?|abs|acosh?|asinh?|atanh?|exp|log10|deg2rad|rad2deg|sqrt|ceil|floor|round)';
    $operators = '[+\/*\^%-]';
    $regexp = '/^(('.$number.'|'.$functions.'\s*\((?1)+\)|\((?1)+\))(?:'.$operators.'(?2))*)+$/';

    if (preg_match($regexp, $q))
    {
        $q = strtr($q, array(',' => '.', 'pi' => 'pi()', 'π' => 'pi()'));

        eval('$ret = (float) '.$q.';');

        return $ret;
    }

    return false;
}

?>