Thread:Project:Support desk/wfProfileIn( METHOD . '-replace' ); what does it mean?

I have the code  in an extension (Replace Text). What does it mean? I'm trying to change the following code to use preg_replace_callback instead and it won't work. I'm wondering if this is connected to wfProfileIn( __METHOD__ . '-replace' ); even if I set  nothing happens in the code. Why can I only use preg_replace? What am I missing here? The file is extensions/ReplaceText/ReplaceTextJob.php line 95.