String as an Expression

cjones

Hello,

I'm kind of stuck on a problem right now. I need to find a way to take a string as an expression.

Example:

$num = 4;
$string = "2 * $num + 5";

Is there anyway to evalute $string to return the answer? hopefully without parsing it character by character. =]

I thought of another way by storing the posted string to a file so the file would look like this:

<?php $string = 2 * $num + 5; ?>

I just include the file and it does the trick. This work with me just testing but it won't work well in a multi-user environment due to the file being overwritten before it's recalled by the user needing it.

Thanks in advance,
Chris Jones

Anon

You mean something that will output 13?

2*4 = 8
8 + 5 = 13?

If so just do...

<?php
$num = 4;
$string = (2 * $num + 5);
echo $string;
?>

cjones

I guess I didn't expalin it right.

I'm going to have a form with a field called expression. In this textbox the user can put in any expression using $num.

So one could enter:

2 * $num + 5

another could enter:

($num / 5 * 10) + 22

etc.

When the user submits the POST then I will have a string varible $expression that equals whatever they typed.

For example lets say :

"2 * $num + 5"

now how can I execute this as an expression and not a string to get the answer?

$num is going to be a for loop varible. Say from 0 to 10.

Thanks,
Chris Jones

cjones

nevermind ..... I think I found a solution using the eval function. =]