What are the differences between using an absolute URL and a relative URL in the header(location: $url) function?

When using the header(location: $url) function in PHP to redirect to a different page, you can specify the URL as an absolute URL or a relative URL. An absolute URL includes the full path to the destination page (e.g., https://example.com/page.php), while a relative URL only includes the path relative to the current page (e.g., page.php). To ensure compatibility and avoid potential issues with redirects, it is recommended to use absolute URLs when redirecting to external websites or when the destination page is on a different domain. For internal redirects within the same domain, relative URLs can be used.

// Redirect using an absolute URL
header("Location: https://example.com/page.php");

// Redirect using a relative URL
header("Location: page.php");