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];
 }