Process mathematical equations in php

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My standard answer to this question whenever it crops up:

Don’t use eval (especially as you’re stating that this is user input) or reinvent the wheel by writing your own formula parser.

Take a look at the evalMath class on PHPClasses. It should do everything that you’ve listed here.

EDIT

re: Unfortunately evalMath does not handle things like (x > 5)

change lines 177-179 to

$ops   = array('+', '-', '*', "https://stackoverflow.com/", '^', '_', '>', '<', '=');
$ops_r = array('+'=>0,'-'=>0,'*'=>0,"https://stackoverflow.com/"=>0,'^'=>0, '>' => 0, '<' => 0, '=' => 0); // right-associative operator?
$ops_p = array('+'=>0,'-'=>0,'*'=>1,"https://stackoverflow.com/"=>1,'_'=>1,'^'=>2, '>' => 0, '<' => 0, '=' => 0); // operator precedence

change line 184 to

if (preg_match("/[^\w\s+*^\/()\.,-<>=]/", $expr, $matches)) { // make sure the characters are all good

add

case '>':
     $stack->push($op1 > $op2); break;
case '<':
     $stack->push($op1 < $op2); break;
case '=':
     $stack->push($op1 == $op2); break;

after line 321

and evalMath will now handle (x > 5), (x < 5) or (x = 5)

// instantiate a new EvalMath
$m = new EvalMath;
$m->suppress_errors = true;
// set the value of x
$m->evaluate('x = 3');
var_dump($m->evaluate('y = (x > 5)'));

Further Edit

Missed line 307 that should be modified to read:

if (in_array($token, array('+', '-', '*', "https://stackoverflow.com/", '^', '>', '<', '='))) {

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