The MySQL extension for PHP must be loaded correctly through the php.ini Especially on Windows platforms, this can be rather troublesome as there are multiple locations where libmysql.dll file can be placed (PHP directory, MySQL directory, Windows system directories) Adding a phpinfo file to your installation (a file with just the contents:
echo phpinfo();
?>
) can help you track down whether this extension is correctly loaded. Unfortunately the documentation is lacking in this area, but it is an Apache/MySQL problem and not specific to using XOOPS
PHP 5.0.x
Php 5.0.x users get this error because mysql extensions are no more loaded for default in the php distribution.
You may load mysql extensions manually as server module. On Apache servers, you may modify httpd-config file. Read php 5.0.x installation notes for further detalis.