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?
- @hakre: how about javascript version?IRvanFauziE– IRvanFauziE2013-09-25 06:54:46 +00:00Commented Sep 25, 2013 at 6:54
- 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 Javascripthakre– hakre2013-09-25 07:26:42 +00:00Commented Sep 25, 2013 at 7:26
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5 Answers
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.
1 Comment
IRvanFauziE
thanks ur the winner for Javascript version :)
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
1 Comment
IRvanFauziE
thanks ur the winner for PHP version :)
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 $res; 
Comments
Something like this should work in PHP and javascript(with a little modification). Also I'd recommend not using eval what so ever because of security reasons.
function math($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 
Comments
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.'
