初学黑客：php获取服务器路径及访客信息

<?php
echo "php获取当前url<br/>";
$url =  "http://".$_SERVER ['HTTP_HOST'].$_SERVER['PHP_SELF'];
echo $url;
?>

<br/>以下代码是：php获取网站根目录<br/>

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

<br/>php获取访客信息<br/>

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