php获取访客ip地址的方法

 function ip() { 
if(getenv('HTTP_CLIENT_IP') && strcasecmp(getenv('HTTP_CLIENT_IP'), 'unknown')) { 
$ip = getenv('HTTP_CLIENT_IP'); 
} elseif(getenv('HTTP_X_FORWARDED_FOR') && strcasecmp(getenv('HTTP_X_FORWARDED_FOR'), 'unknown')) { 
$ip = getenv('HTTP_X_FORWARDED_FOR');
 } elseif(getenv('REMOTE_ADDR') && strcasecmp(getenv('REMOTE_ADDR'), 'unknown')) { 
$ip = getenv('REMOTE_ADDR'); 
} elseif(isset($_SERVER['REMOTE_ADDR']) && $_SERVER['REMOTE_ADDR'] && strcasecmp($_SERVER['REMOTE_ADDR'], 'unknown')) { 
$ip = $_SERVER['REMOTE_ADDR']; 
} 
return preg_match("/[\d\.]{7,15}/", $ip, $matches) ? $matches[0] : 'unknown'; 
}
?>