PHP获取访问者IP

方法一：$_SERVER['HTTP_X_FORWARDED_FOR']来获取相应的地址

 function get_onlineip() {
     $onlineip = '';
     if(getenv('HTTP_CLIENT_IP') && strcasecmp(getenv('HTTP_CLIENT_IP'), 'unknown')) {
         $onlineip = getenv('HTTP_CLIENT_IP');
     } elseif(getenv('HTTP_X_FORWARDED_FOR') && strcasecmp(getenv('HTTP_X_FORWARDED_FOR'), 'unknown')) {
         $onlineip = getenv('HTTP_X_FORWARDED_FOR');
     } elseif(getenv('REMOTE_ADDR') && strcasecmp(getenv('REMOTE_ADDR'), 'unknown')) {
         $onlineip = getenv('REMOTE_ADDR');
     } elseif(isset($_SERVER['REMOTE_ADDR']) && $_SERVER['REMOTE_ADDR'] && strcasecmp($_SERVER['REMOTE_ADDR'], 'unknown')) {
         $onlineip = $_SERVER['REMOTE_ADDR'];
     }
     return $onlineip;
 }

方法二：利用curl依靠第三方来获取，如http://www.ip138.com/ip2city.asp

 function get_onlineip() {
     $ch = curl_init('http://www.ip138.com/ip2city.asp');
     curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
     $a  = curl_exec($ch);
     preg_match('/\[(.*)\]/', $a, $ip);
     return $ip[1];
  }