Regex - strip all non alpha-num

[OhLordy]

Hi, I need a regex to strip out all non alphanumeric characters from a string but I'm rubbish at them. I have written the following function but I'm sure that there must be a way of doing it with preg that would be a lot quicker.

<?
function makeAlNum($word)
{
    $newword="";
    for($i=0;$i<strlen($word);$i++) {
        if(preg_match("/[a-zA-Z0-9]/",substr($word,$i,1))) {
            $newword.=substr($word,$i,1);
        }
    }
    return $newword;
}
?>

Thanks in advance
Rob

[drawmack]

preg_replace("/![a-zA-Z0-9]/eeg","",$var);