How to implement online netizens in php_PHP tutorial

$time=getdate();
$tt=$time[year]*365*24*60+$time[mon]*30*24*60+$time[mday] *24*60+$time[hours]*60+$time[minutes];
if($userid!="guest"){
$SQLqq="UPDATE $USER_ATTR_TABLE SET time=$tt,status =1 WHERE userid=$userid";
mysql_query($SQLqq);}
$SQLq="SELECT status,userid,time FROM $USER_ATTR_TABLE WHERE status=1;";
$resultq=mysql_query( $SQLq) or die(mysql_error());
$countq=mysql_numrows($resultq);
for ($ii=0;$ii $rowq=mysql_fetch_Array ($resultq);
$useridq=$rowq[userid];
$times=$rowq[time];
$ts=$tt-$times;
if($ts>= 15)
{
$sqls="UPDATE $USER_ATTR_TABLE SET status=0 WHERE userid=$useridq";
mysql_query($sqls); } }?>I write down the code and the rest is It’s up to you:) If you don’t understand anything, you can ask me. I’m always here:)