PHP $_SERVER[] 變數

<?php
echo "\$_SERVER['PHP_SELF'] : " .$_SERVER['PHP_SELF']."<br>";
echo "\$_SERVER['SERVER_NAME'] : " .$_SERVER['SERVER_NAME']."<br>";
echo "\$_SERVER['DOCUMENT_ROOT'] : " .$_SERVER['DOCUMENT_ROOT']."<br>";
echo "\$_SERVER['SCRIPT_FILENAME'] : " .$_SERVER['SCRIPT_FILENAME']."<br>";
echo "\$_SERVER['SCRIPT_NAME'] : " .$_SERVER['SCRIPT_NAME']."<br>";
echo "\$_SERVER['HTTP_USER_AGENT']: " .$_SERVER['HTTP_USER_AGENT']."<br>";
echo "\$_SERVER['QUERY_STRING'] : " .$_SERVER['QUERY_STRING']."<br>";    
echo "\$_SERVER['REMOTE_PORT']  : " .$_SERVER['REMOTE_PORT']."<br>";          
?>

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$_SERVER['PHP_SELF'] : /PM-4/p4-3.php
$_SERVER['SERVER_NAME'] : 127.0.0.1
$_SERVER['DOCUMENT_ROOT'] : C:/Program Files/EasyPHP-12.1/www
$_SERVER['SCRIPT_FILENAME'] : C:/Program Files/EasyPHP-12.1/www/PM-4/p4-3.php
$_SERVER['SCRIPT_NAME'] : /PM-4/p4-3.php
$_SERVER['HTTP_USER_AGENT']: Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/34.0.1847.131 Safari/537.36
$_SERVER['QUERY_STRING'] : a=1&b=2
$_SERVER['REMOTE_PORT'] : 65318