實例：

1，http://localhost/aaa/ (打開aaa中的index.php)
結果：
$_SERVER[‘QUERY_STRING‘] = "";
$_SERVER[‘REQUEST_URI‘] = "/aaa/";
$_SERVER[‘SCRIPT_NAME‘] = "/aaa/index.php";
$_SERVER[‘PHP_SELF‘] = "/aaa/index.php";

2，http://localhost/aaa/?p=222 (附帶查詢)
結果：
$_SERVER[‘QUERY_STRING‘] = "p=222";
$_SERVER[‘REQUEST_URI‘] = "/aaa/?p=222";
$_SERVER[‘SCRIPT_NAME‘] = "/aaa/index.php";
$_SERVER[‘PHP_SELF‘] = "/aaa/index.php";

3，http://localhost/aaa/index.php?p=222&q=333
結果：
$_SERVER[‘QUERY_STRING‘] = "p=222&q=333";
$_SERVER[‘REQUEST_URI‘] = "/aaa/index.php?p=222&q=333";
$_SERVER[‘SCRIPT_NAME‘] = "/aaa/index.php";
$_SERVER[‘PHP_SELF‘] = "/aaa/index.php";

由實例可知：
$_SERVER["QUERY_STRING"] 獲取查詢 語句，實例中可知，獲取的是?後面的值
$_SERVER["REQUEST_URI"] 獲取 http://localhost 後面的值，包括/
$_SERVER["SCRIPT_NAME"] 獲取當前腳本的路徑，如：index.php
$_SERVER["PHP_SELF"] 當前正在執行腳本的文件名

【轉載】詳解 $_SERVER 函數中QUERY_STRING和REQUEST_URI區別