PHP 使用 Apache WWW-Authenticate 認證身份

<?php
$user = '認證帳號';
$pw = '認證密碼';

if(!isset($_SERVER['PHP_AUTH_USER']) || $_SERVER['PHP_AUTH_PW']=='') {
    Header("WWW-Authenticate: Basic realm=\"login\"");
    Header("HTTP/1.0 401 Unauthorized");
    die('認證失敗');
} else {
    if($_SERVER['PHP_AUTH_USER']!=$user || $_SERVER['PHP_AUTH_PW']!=$pw) {
        Header("WWW-Authenticate: Basic realm=\"login\"");
        Header("HTTP/1.0 401 Unauthorized");
        die('帳號或密碼錯誤');
    }
}

echo "認證成功";