1.PHP Manual related to zlib extension [1], did not show ob_gzhandler() function that was linked to the Output Control Functions [2].
Answer came from Reflection API 2.Specific versions.xml extension file [3], did not show ob_gzhandler() (since PHP 4.0.4) and readgzfile() functions.
Laurent [1] http://www.php.net/manual/en/book.zlib.php [2] http://www.php.net/manual/en/ref.outcontrol.php [3] http://cvs.php.net/viewvc.cgi/phpdoc/en/reference/zlib/versions.xml