Log base 2 in PHP

I need to find the log base 2 of a number. Is there a built in PHP function that can help? I was only able to find log base E or log base 10.
Thanks...

 

I got it. Sorry.
The answer I came up with is:

function Log2($x){
return (log10($x) / log10(2));
}

Can anyone think of a better solution?

 

http://www.php.net/log

echo log($argument, 2);

PHP:

Jay