What is the difference between QUERY_STRING and REQUEST_URI in PHP?

QUERY_STRING refers to the query string portion of the URL, which includes the parameters passed to the script. REQUEST_URI, on the other hand, refers to the full URL path including the query string. If you need to access only the parameters passed to the script, you should use QUERY_STRING. If you need to access the full URL path including the query string, you should use REQUEST_URI.

// Using QUERY_STRING to access parameters passed to the script
$queryString = $_SERVER['QUERY_STRING'];

// Using REQUEST_URI to access the full URL path including the query string
$requestUri = $_SERVER['REQUEST_URI'];