初學黑客：php獲取服務器路徑及訪客信息

<?php
echo "php獲取當前url<br/>";
$url =  "http://".$_SERVER ['HTTP_HOST'].$_SERVER['PHP_SELF'];
echo $url;
?>

<br/>以下代碼是：php獲取網站根目錄<br/>

<?php
$PHP_SELF=$_SERVER['PHP_SELF'];
$url='http://'.$_SERVER['HTTP_HOST'].substr($PHP_SELF,0,strrpos($PHP_SELF,'/')+1);
echo $url;
?>
-->

<br/>php獲取訪客信息<br/>

<?php
print_r($_SERVER['CERT_SERIALNUMBER']);
print_r($_SERVER);
 ?>