Display TIMEDIFF result from mySQL query to webpage - php

Question

Me again, guys. The titles is pretty self-explanatory, but for the details:
I want to display the timediff(in hours) results on a webpage but I can't wrap my head around how to do it.
I'm using PHP and Codeigniter for this website.
So far, I have a mySQL database with a table named 'server_log' which looks like:
+--------+-----------+--------+---------+------------+-------------+
| log_id | host_name | status | host_id | profile_id | event_date |
+--------+-----------+-+----------------+------------+-------------+
| 1 | http://...| Online | 1 | 1 | *timestamp* |
+--------+-----------+--------+---------+--------------------------+
*It shows also other entries with status "Offline" and "Maintenance".
I have this query to get the entries per user (based on profile_id) w/c are also sorted by status ('Online','Offline', or 'Maintenance'):
SELECT * FROM server_log
WHERE (profile_id=$id AND status='Online')
AND event_date BETWEEN $from_date AND $to_date
ORDER BY event_date,host_id;
*the from_date and to_date are results from the webpage which lets the user choose a 'From' and 'To' date to filter the results like a report page.
The problem I have is that after the above query I do not know what I else I need in order to calculate the TIMEDIFF results for each server(host_id) then display them on the webpage. (I'd like to get the TIMEDIFF between the results after getting the query results for each status)
How do I get the TIMEDIFF result (integer)?
Simply put, I want the flow to be like this:
[1] After 1st query: (SELECT ALL 'Online' for $id)
log_id | host_name | status | host_id | profile_id | event_date
1 ping.test1 Online 1 2 **
2 ping.test1 Online 1 2 **
3 ping.test2 Offline 2 2 **
4 ping.test2 Offline 2 2 **
[2] After 2nd query: (loop for each host_id)
log_id | host_name | status | host_id | profile_id | event_date
1 ping.test1 Online 1 2 **
2 ping.test1 Online 1 2 **
-> then calculate diff_date of event_dates
---> then return value to be assigned to $data['reports_ping']
-----> back to [1] but selecting all 'Offline', then 'Maintenance'
-------> if all values are assigned, display $data['reports_ping'] as row (foreach)
I would like the results to show something like:
+------------+------------+------------+-------------+-------------+
| profile_id | host_name | online_hrs | offline_hrs | maintenance |
+------------+------------+------------+-------------+-------------+
| 1 | http://... | 2 | 1 | 0 |
+------------+------------+------------+-------------+-------------+
I'm relatively a beginner and not really that good with CodeIgniter, so any help with this would be REALLY appreciated. Thanks in advance!

Answer 1

TIMEDIFF meaning different time between event_date and now? Try this :
SELECT *, (event_date - NOW()) as TIMEDIFF FROM server_log
WHERE (profile_id=$id AND status='Online')
AND event_date BETWEEN $from_date AND $to_date
ORDER BY 'event_date','host_id';
-- EDIT --
Is this the logic you want?
$temp = null;
foreach($rows){
$event_date = "select event_date from server_log order by log_id LIMIT 1"; // specify this query using your CI format
$timediff = $event_date - $temp;
$temp = $event_date;
}