X-Cart/Smarty Custom PHP Scripts

[empiresolutions]

i have what may be a very simple question for someone who has worked with X-Cart or Smarty.

I am adding a rollover image next to the category names in the main navigation. The following is my stripped down for this post version.
[php]
{foreach from=$categorie s item=c}

<div>

<div><img name="{$c.categ ory}_" src="{$ImagesDi r}/custom/paw.gif"></div>
<div><a href="home.php? cat={$c.categor yid}">{$c.categ ory}</a></div>

</div>

{/foreach}
[/php]I need to remove spaces in the names given at

name="{$c.category}_"

I want to make it

name="{str_replace(" ","_",$c.category)}_"

My attempts don't work and I get this error

Error: Smarty error: [in customer/categories.tpl line 26]: syntax error: unrecognized tag: str_replace(" ","_",$c.catego ry) (Smarty_Compile r.class.php, line 436) in C:\apache2triad \htdocs\clients \sitename.com\w ww\Smarty-2.6.12\Smarty.c lass.php on line 1095

My question is.. How can I make PHP functions work in X-Cart/Smarty?

I cant even find where $c.category is set. Thanks much.

[empiresolutions]

Thanks Jay. Here's the solution-

{$c.category|replace:" ":""}

im now finding that slashes are not allowed either.

{$c.category|replace:" ":""|replace:"/":""}

works too. sweet.