php常用预定义变量

<?php 
echo $_SERVER['REMOTE_ADDR'];echo"<br />";
echo $_SERVER['PHP_SELF'];echo"<br />";
echo $_SERVER['DOCUMENT_ROOT'];echo"<br />";
echo $_SERVER['SCRIPT_FILENAME'];echo"<br />";
echo $_SERVER['SCRIPT_NAME'];echo"<br />";
echo $_SERVER['SERVER_NAME'];echo"<br />";