note 114272 added to function.eval

Modified version of bohwaz's answer: with negative number support and removes the requirement of properly grouped (bracketed) expressions. <?php function calc($equation) { // Remove whitespaces $equation = preg_replace('/\s+/', '', $equation); echo "$equation\n"; $number = '(?:-?\d+(?:[,.]\d+)?|pi|π)'; // What is a number $functions = '(?:sinh?|cosh?|tanh?|abs|acosh?|asinh?|atanh?|exp|log10|deg2rad|rad2deg|sqrt|ceil|floor|round)'; // Allowed PHP functions $operators = '[+\/*\^%-]'; // Allowed math operators $regexp = '/^(('.$number.'|'.$functions.'\s*\((?1)+\)|\((?1)+\))(?:'.$operators.'(?1))?)+$/'; // Final regexp, heavily using recursive patterns if (preg_match($regexp, $equation)) { $equation = preg_replace('!pi|π!', 'pi()', $equation); // Replace pi with pi function echo "$equation\n"; eval('$result = '.$equation.';'); } else { $result = false; } return $result; } ?> ---- Server IP: 192.41.45.150 Probable Submitter: 207.237.150.246 ---- Manual Page -- http://php.net/manual/en/function.eval.php Edit -- https://master.php.net/note/edit/114272 Del: integrated -- https://master.php.net/note/delete/114272/integrated Del: useless -- https://master.php.net/note/delete/114272/useless Del: bad code -- https://master.php.net/note/delete/114272/bad+code Del: spam -- https://master.php.net/note/delete/114272/spam Del: non-english -- https://master.php.net/note/delete/114272/non-english Del: in docs -- https://master.php.net/note/delete/114272/in+docs Del: other reasons-- https://master.php.net/note/delete/114272 Reject -- https://master.php.net/note/reject/114272 Search -- https://master.php.net/manage/user-notes.php