We use the following function to auto detect if we are on a machine internally or on a live server and then choose the appropriate configs for various components.

function devIsLocal(){

    $res=false;

    $http_host=$_SERVER['HTTP_HOST'];

    if($http_host=='localhost')$res=true;
    if($http_host=='127.0.0.1')$res=true;
    if(substr($http_host,-4)=='.lan')$res=true;
    if(strpos($http_host, '.')===false)$res=true;

    return($res);

}

As you can see it only relies on the HTTP_HOST value.

Of course, if you have use virtual host locally like example.com then the function will be tricked.

Are there any other ways to fool the function? and what other variables/places could we peek at to determine where we are?