What is the difference between $_SERVER["QUERY_STRING"] and REQUEST_URI in PHP?

$_SERVER["QUERY_STRING"] contains the query string (parameters) of the URL, while REQUEST_URI contains the URI of the current request. If you need to access the query string parameters specifically, you would use $_SERVER["QUERY_STRING"]. If you need the entire URI including the query string, you would use REQUEST_URI.

// Using $_SERVER["QUERY_STRING"] to access query string parameters
$queryString = $_SERVER["QUERY_STRING"];

// Using REQUEST_URI to access the entire URI including the query string
$uri = $_SERVER["REQUEST_URI"];