Calculate an inputted string?

[Gary_King]

How can I create an input text area, where someone can type in a string to calculate, such as:

code*9/6 (outputs 3)[/code]

I can't seem to get PHP to do that. Any ideas?

[drew010]

try using eval()

$string = "(1+1)*9/6";

echo eval($string);

[Gary_King]

I've tried using eval(), and it still just outputs whatever was inputted.

[drew010]

ok yeah i get an error too. i didnt test it.. ive tried a few things and cant get anything to work 🙁

[Gary_King]

Use

eval("return \$string;")

But like I said, it will only return whatever it was given.

I had already tried searching for a PHP calculator like this, but I couldn't find one. I don't believe it's not possible - it must be, but how? 😕

[HalfaBee]

Originally posted by Gary W
Use

eval("return \$string;")

But like I said, it will only return whatever it was given.

I had already tried searching for a PHP calculator like this, but I couldn't find one. I don't believe it's not possible - it must be, but how? 😕 [/B]

Of course it is possible, everything is possible in PHP! 🙂

Try this

<?
$string = "(1+1)*2";
$s = "\$i = $string";
echo eval( "$s;return \$i;" );
?>

HalfaBee

[drew010]

sure the last example works, but try doing that from POSTed data in a form.. it then fails.

[HalfaBee]

Works fine!
Try this.

<?
$string = $_POST['string'];
echo eval( "\$i = $string;return \$i;" );
?>
<FORM method=post >
<input name=string >
<input type=submit >
</FORM>

[HalfaBee]

echo eval ( "return $string" );

works just as well.

HalfaBee

[Gary_King]

My final result:

http://personal.torontoview.com/calculate.php

And oh, the code for displaying the calculation result is the following:

if ($_POST['calculate'])
{
	$string=$_POST['string'];
	print "<b>Result:</b> ".eval("return $string;");
}

🙂

[HalfaBee]

You should do some checking to secure your input.

if( !preg_match( "/[(*-+0-9).\/]+/" ,$string ) )
echo 'No way am I doing that';
else
echo eval( "return $string;" );

What would happen if I typed in unlink( ".") ?

HalfaBee

[Gary_King]

It wouldn't work 😉

[HalfaBee]

what about unlink(script.php)?

HalfaBee

[Gary_King]

As I said, it won't work.

[HalfaBee]

Ohh. The links not there!
I wonder why? 🙂

[Gary_King]

Originally posted by HalfaBee
Ohh. The links not there!
I wonder why? 🙂

Because it's here now:

http://personal.torontoview.com/temp/calculate.php 😃