- trim: documentation ( source)
- preg_replace: documentation ( source)
<?php
function calc_string($string) {
$calc = create_function("", "return (" . preg_replace('[^0-9\+-\*\/\(\) ]', '', trim($string)) . ");" );
return $calc();
}
echo calc_string("6 * ((26 / 2) + -3) - 20");