How do I solve this error, showing in http logs?
Erro: an unknown filter was not added: PHP
You don't say exactly what your setup is, but I would first check your apache/php installation. Check the compatibility notes on the PHP site...
http://www.php.net/manual/en/install.apache2.php
(assuming Apache2 of course)
http://www.php.net/manual/en/install.apache2.php
(assuming Apache2 of course)