PHP - Multiple Time Difference Calculations - php

Question

For the life of me I cannot find anywhere on the internet that has any documentation on how to solve my problem. I've seen a massive amount of ways to calculate differences in time but I can not seem to put something together that works for my situation.
I'm currently building a time management/ticket system that is a plugin for WordPress. I am using custom tables and not the WordPress tables. I have a table that contains all the main ticket information and another table that contains all the start/stop times. Once the user marks the ticket as complete it will then take all the start/stop time values and calculate the total time spent and then place that total time value into a "total_time" column in the main ticket table.
I'm querying the database and pulling the start/stop times by using:
$start_times = $wpdb->get_results($start_times_query);
$stop_times = $wpdb->get_results($stop_times_query);
Now I have the information in 2 array's. Is this the way I should be doing this?
The array's give me this (for start times):
Array ( [0] => Array ( [time] => 2016-04-29 12:02:43 ) [1] => Array ( [time] => 2016-04-29 12:04:18 ) [2] => Array ( [time] => 2016-04-29 12:06:07 ) [3] => Array ( [time] => 2016-04-29 12:07:56 ) [4] => Array ( [time] => 2016-04-29 12:10:30 ) [5] => Array ( [time] => 2016-04-29 12:11:59 ) )
(Same format for the end times)
Then I break down the array using:
$startTimes = array_column($startTimes, 'time');
$endTimes = array_column($endTimes, 'time');
Which now gives me this as the array (this one is just the start times, but same format for the end times):
Array ( [0] => 2016-04-29 12:02:43 [1] => 2016-04-29 12:04:18 [2] => 2016-04-29 12:06:07 [3] => 2016-04-29 12:07:56 [4] => 2016-04-29 12:10:30 [5] => 2016-04-29 12:11:59 )
Usually I can do a foreach ($start_time as $time){} to itterate through all the values, but (correct me if I'm wrong) I can't put two array's into the foreach brackets and I can't place another foreach statement in the current one because then it will just return all the times for the second array and only return one value for the first array. I feel like I'm missing something simple, what can I do to accomplish this?
EDIT
Thanks to Scopey I've worked out a while loop, but it's not functioning correctly. Here is what I have:
$startTimes = array_column($startTimes, 'time');
$endTimes = array_column($endTimes, 'time');
while (($startTime = current($startTimes)) !== false && ($endTime = current($endTimes) !== false)) {
$startTimesConv = strtotime($startTimes);
$endTimesConv = strtotime($endTimes);
$totalTime = ($startTimesConv - $endTimesConv)/60/60;
next($startTimes);
next($endTimes);
}

Answer 1

If you want to loop two arrays at the same time, you can use the PHP functions for traversing arrays by manipulating their internal pointer: current, next, reset, end and prev.
You just need to make a while loop:
while (($startTime = current($startTimes)) !== false && ($endTime = current($endTimes) !== false) {
// ... Do things
next($startTimes);
next($endTimes);
}
See the documentation for next and current

Answer 2

To iterate two regular arrays with the same length use for instead of foreach:
$length = count($start_times);
for ($i = 0; $i < $length; $i++) {
$start_time = $start_times[$i]["time"];
$stop_time = $stop_times[$i]["time"];
// do things
}
But in your case, I strongly recommend that calculate the differences in SQL.

Answer 3

I would take a step back and look at the queries themselves. You are trying to do a calculation between two times which are related in your database however, the relationship gets lost by separating the times into two separate arrays. Or at the very least is ambiguously related as an array index.
My pseudocode would look like this:
#For each ticket which is closed
#Get an array (time entries) of arrays (start, stop) (each having it's start and stop time)
#total_time = 0
#For each time entry
#Perform a time calc function to get_time_differnce(start, stop)
#Add the time to Total_time
#Add total_time to ticket record in DB
If you showed some more detail I might be able to expand. (i.e The queries themselves)