Javascript/PHP Custom math formula

Question

can we use math formula from other variable/database? example:

var x = 7;
var formula = '+';
var y = 10;

I mean that variables will output = 17 (7 + 10);

but how to implement this formula using Javascript/PHP?

Please use the search. Also if you look for javascript, you should not tag as PHP. - possible duplicate of: [Safe evaluation of arithmetic expressions in Javascript](http://stackoverflow.com/q/5066824/367456) — hakre, Sep 25 '13 at 07:26

score 1 · Accepted Answer · answered Sep 25 '13 at 05:22

1

For your example you could do this:

var x = 7;
var formula = '+';
var y = 10;
z = eval(x+formula+y);  // 17
document.write(z);

But eval is a big problem for security, and you really shouldn't use it. If you could give more detail on what you're trying to achieve it might be possible to suggest an alternative.

answered Sep 25 '13 at 05:22

thanks ur the winner for Javascript version :) – IRvanFauziE Sep 25 '13 at 06:53

score 1 · Answer 2 · answered Sep 25 '13 at 05:25

1

PHP Version

use eval() in php to run a php code segment:

<?php
$x = 7;
$formula = '+';
$y = 10;
$expression = '$result = ' .$x . ' ' . $formula . ' ' . $y . ";";
echo $expression, "\n";    // $result = 7 + 10;
eval($expression);         // run the code
echo $result, "\n";        // ouput 17

see the result of the code here

answered Sep 25 '13 at 05:25

srain

8,944
6
30
42

thanks ur the winner for PHP version :) – IRvanFauziE Sep 25 '13 at 06:52

score 0 · Answer 3 · answered Sep 25 '13 at 05:29

0

In php you can use as below. You can avoid eval in this way.

$x = 7;
$formula = '+';
$y = 10;

switch ($formula) {

case "+" : $res = $x + $y;
          break;

case "-" : $res = $x - $y;
          break;

.
.
.
.


}

echo $res;

answered Sep 25 '13 at 05:29

sandy

1,126
1
7
17

score 0 · Answer 4 · answered Sep 25 '13 at 05:32

Something like this should work in PHP and javascript(with a little modification). Also I'd recommend not using eval what so ever because of security reasons.

function math($x, $y, $sign){
    switch($sign){
        case '+':
            return $x + $y;
        case '-':
            return $x - $y;
        case '*':
            return $x * $y;
        case '/':
            return $x / $y;
        default:
            return;
    }
}
$x = 7;
$formula = '+';
$y = 10;
echo math($x, $y, $formula);#returns 17

score 0 · Answer 5 · answered Sep 25 '13 at 05:36

If you'll be evaluating textual formulas repeatedly with 'eval(),' you may wish to store it within a function - like this:

var formula = "x + y";
var func;
eval("func = function(){return" + formula + "}");

At this point, you could call 'func()' at any time when variables x and y exist within the given scope. For example:

var x = 7;
var y = 10;
var answer = func();

The value of answer would then be '17.'

Javascript/PHP Custom math formula

5 Answers5

PHP Version

see the result of the code here