XML : creating more than one string replace

I'm trying to change multiple lines in a template. I use vBulletin software.

This is what I have:

  $drcidl_inc = '<!-- / CSS Stylesheet -->';  $drcidl_cr = '$vbphrase[powered_by_vbulletin]';  $drcrb_hd = '<textarea name=\"message\" id=\"{$editorid}_textarea\" rows=\"10\" cols=\"60\" style=\"width:100%; height:{$editor_height}px\" tabindex=\"1\" dir=\"$stylevar[textdirection]\"></textarea>';  $find = '<textarea name=\"message\" id=\"{$editorid}_textarea\"';  $replace = '<textarea class=\"form-control comment-form-textarea\" name=\"message\" id=\"{$editorid}_textarea\"';  if(strpos($vbulletin->templatecache['headinclude'],$drcidl_inc) !==false)$vbulletin->templatecache['headinclude'] = str_replace($drcidl_inc,fetch_template('drc_iiu_css').$drcidl_inc,$vbulletin->templatecache['headinclude']);  else $vbulletin->templatecache['headinclude'] .= fetch_template('drc_iiu_css');  $vbulletin->templatecache['showthread_quickreply'] = str_replace($find,$replace,$vbulletin->templatecache['showthread_quickreply']);  $vbulletin->templatecache['showthread_quickreply'] = str_replace($drcrb_hd,$drcrb_hd.fetch_template('drc_iiu_below_txtarea'),$vbulletin->templatecache['showthread_quickreply']);  $vbulletin->templatecache['footer'] = str_replace($drcidl_cr,$drcidl_cr.fetch_template('drc_iiu_js'),$vbulletin->templatecache['footer']);    

This works but only the first showthread_quickreply str_replace is functioning. I'm not sure exactly how to phrase this question, but how can I use multiple str_replace's on one ...variable?

This is the one I'm trying to merge:

  $vbulletin->templatecache['showthread_quickreply'] = str_replace($find,$replace,$vbulletin->templatecache['showthread_quickreply']);  $vbulletin->templatecache['showthread_quickreply'] = str_replace($drcrb_hd,$drcrb_hd.fetch_template('drc_iiu_below_txtarea'),$vbulletin->templatecache['showthread_quickreply']);    

and I will need to add another one to it still too.