方法六：
<?php
if(getenv('HTTP_CLIENT_IP')){
$onlineip = getenv('HTTP_CLIENT_IP');
}
elseif(getenv('HTTP_X_FORWARDED_FOR')){
$onlineip = getenv('HTTP_X_FORWARDED_FOR');
}
elseif(getenv('REMOTE_ADDR')){
$onlineip = getenv('REMOTE_ADDR');
}
else{
$onlineip = $HTTP_SERVER_VARS['REMOTE_ADDR'];
}
echo $onlineip;
?>