Prompt the decision of my problem

Hello! Prompt the decision of my problem. I do a site, and I use sheaf XML + XSLT (all files in the coding utf-8), under Windows. A problem: at the established coding of a conclusion in a xslt-pattern distinct from utf-8, for example windows-1251 I receive symbols BOM in a conclusion of the buffer. To get rid of it to me function does not help: ob_start ('ob'); function ob ($buffer) { //kill byte order mark $buffer = preg_replace ('@\xef\xbb\xbf@', ", $buffer); return trim ($buffer); } It is very strange as if to check so: $firstchar = substr ($buffer, 0, 1); the first symbol will be < - in my case it <! DOCTYPE ht..., that is after work of a method transformToXML in a conclusion it is impossible to define presence BOM (and it there is)! As the conclusion turns out in the coding windows-1251, and in the buffer remains BOM a browser breaks display, including what it to it has come utf-8. It is inconvenient me manually delete BOM from files php as periodically I hands correct them in a notepade for windows. Why it is not visible BOM in buffer?