RegEx matching in Javascript?

[Jaxel]

Okay... I have set up a test page... (IE only)
http://www.8wayrun.com/test.html

It uses 2 other files... the test.JS file (link on the page above), and a test.PHP file: contents below:

<?php

$field = explode('_',$_GET['fieldname']);
$input = $_GET['content'];

if ($field[0] == "score") { update_score($field,$input); }

function update_score($field,$input)
{
	global $vbulletin, $thumbdir;

	$input = str_replace(' ','',$input);
	$input = strtolower($input);

	if (!$input) { echo '&nbsp;'; exit; }
	$uses = explode(',',$input);

	foreach ($uses as $use)
	{
		$usage .= '<img src="ranking/usage/'.$use.'.gif">';
	}

	echo $usage;
}

?>

If you to that page, you will understand my problem more. If you click on the image bar, it will return the following text: "cas,sig,hil,cer,xia". You can then change the text, for instance, type in "tir,tal,tak". Instead of those 5 previous images, you will get 3 different images. That is working as intended...

Now, click on the image bar again, without refreshing the page. Instead of it returning "tir,tal,tak", it returns an empty text box. This is my problem.