用户状态为“脱机”时的PHP

I been trying to run this function but I am not sure if the php is correct I seem to get it when there are numbers but I am trying to set it = 0. Here is the code:

mysql_connect(db_server, db_user, db_pass);
$res = mysql_db_query(db_name,"SELECT user_time_check FROM user"); 
$setuseroffline = mysql_result($res, 0, 0); 
$setuseroff = $setuseroffline;  

if ($setuseroff = 0) { 
//CODE GOES HERE
}

I think the = 0 is set wrong. But my question is how would I be able to set my a function when my user status is Offline or when my user_time_check = 0?

use '==' not '='.'=' is an assignment operator .

so if ($setuseroff = 0) means that you are assigning 0 to the variable $setuseroff and it will always be false

use:

if ($setuseroff == 0)