On Thu, 2008-04-10 at 13:15 +0100, Richard Heyes wrote: > > First post to this list! I'm trying to figure out how to evaluate a > > string with a mathematical expression and get a result, but without > > using eval() as I'm accepting user input into the string. I don't just > > want addition, subtraction, multiplication and division - I'd like to > > take advantage of other functions like ceil, floor etc.
In reply to my own question, I came up with the following function based on a comment on php.net (http://www.php.net/manual/en/function.eval.php#71045). I had a look at the array returned by get_defined_functions() and the maths functions seem mostly to be grouped (with the exception of the random number stuff). It works on my installation but there's nothing in the documentation about get_defined_functions() returning in a particular order - it would be safer to list each math function but I'm lazy. protected function safe_eval($s) { $funcs=get_defined_functions(); $funcs=$funcs["internal"]; $funcs=array_slice($funcs,array_search("abs", $funcs),array_search("rad2deg",$funcs)-array_search("abs",$funcs)); $sfuncs="(".implode(")(",$funcs).")"; $s=preg_replace('`([^+\-*=/\(\)\d\^<>&|\.'.$sfuncs.']*)`','',$s); if (empty($s)) { return 0; } else { try { eval("\$s=$s;"); return $s; } catch(Exception $e) { return 0; } } } -- PHP General Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php
