https://user:pass@example.com/
         ^     ^
         |     |---> Password
         |
         ----> Username

<?php
    function require_auth() {
        $AUTH_USER = 'user';
        $AUTH_PASS = 'pass';
        header('Cache-Control: no-cache, must-revalidate, max-age=0');
        $has_supplied_credentials = !(empty($_SERVER['PHP_AUTH_USER']) && empty($_SERVER['PHP_AUTH_PW']));
        $is_not_authenticated = (
            !$has_supplied_credentials ||
            $_SERVER['PHP_AUTH_USER'] != $AUTH_USER ||
            $_SERVER['PHP_AUTH_PW']   != $AUTH_PASS
        );
        if ($is_not_authenticated) {
            header('HTTP/1.1 401 Authorization Required');
            header('WWW-Authenticate: Basic realm="Access denied"');
            exit;
        }
    }
    require_auth();
    echo "entered";

?>