How to work with string functions with templates

[ThorstenA]

I want to work with string functions to extract information from a template. For example, I want to have an area from USERCP_SHELL template included in FORUMHOM template and try to do that:

$seachstring_start = '<!-- usercp nav -->';
$searchstring_end = '<!-- / usercp nav -->';


$position_start = strpos('fetch_template('USERCP')', $searchstring_start);
$position_end = strpos('fetch_template('USERCP')', $searchstring_end);


$vbulletin->templatecache['FORUMHOME'] = str_replace('$navbar','$navbar'.substr(fetch_template('USERCP'), $position_start, $position_end),$vbulletin->templatecache['FORUMHOME']);

It's not working, what do I do wrong?