In what situations would it be advisable to use PHP headers for caching, and when might it be better to avoid this approach?

Using PHP headers for caching is advisable when you want to reduce server load and improve website performance by storing a copy of the page on the client's browser or in intermediate caches. This can be particularly useful for static pages or resources that don't change frequently. However, it might be better to avoid caching headers for dynamic content that is updated frequently or personalized for each user, as this could lead to users seeing outdated or incorrect information.

// Set caching headers for static content
$expires = 60*60*24*7; // 1 week
header('Cache-Control: max-age=' . $expires);
header('Expires: ' . gmdate('D, d M Y H:i:s', time() + $expires) . ' GMT');