How can custom CSS be integrated into a PHP forum like CutePHP?

To integrate custom CSS into a PHP forum like CutePHP, you can add a link to an external CSS file in the forum's header file. This CSS file can contain custom styles to override the default forum styles and customize the look and feel of the forum.

// In the header file of CutePHP forum
echo '<link rel="stylesheet" type="text/css" href="custom.css">';