How to calculate the value of an expression?

Question

PHP

There is an input field in which formulas are entered (note 2*cos($rad)), $rad is calculated in the code, you need to assign the value of this expression to the $r variable. eval("$r=".$func.";"); it doesn't work like that, I don't know how to do it differently. (This value is calculated n times in a loop and $rad is always different, respectively). For personal use only, so the insecurity of eval is not important

Answer 1

This is how it works ¯\_(ツ)_/¯

$rad = 0.5;
$formula = '2*cos($rad)';

eval('$r = ' . $formula . ';');
echo $r;