strtotime and weird results when calculating time differences (datetime) - php

Question

I've been trying at this for a bit and can't get the damn code to work.. This is my first post, I've gone through a few, tried a million different ways.. I just want to get the difference in hours, then I'm set, I'll get the rest figured out..
Right now, it's giving me unusual answers (say there's a 2 hour difference, it'll give me 14 as an answer) Pardon my coding, I haven't done this in years and have no real formal training. I'll be as thorough as possible in my comments, and thanks a LOT. Any links appreciated. I have tried a LOT. Using PHP 5.3.something, and am pulling off a Wordpress 3.7.1 database.
Thanks in advance for the help for a beginner. I want to display "Updated x hours ago". Once I have the darned thing displaying the correct result, I'll figure the rest out.
//This is the current date, putting it into strtotime so everything is in the same format. It displays accurately.
$currentDate = date("Y-m-d");
$currentTime = date("H:i:s");
$currentDateHour = date("H", strtotime($currentDate . $currentTime));
// This is the date I'm pulling from the database, it only displays
// when in strtotime for some reason. It displays accurately to what is in the mySQL DB
$upDate = date("Y-m-d H", strtotime($row2[post_date]));
// Some variables to make life easier for later if statements if I ever get that far. Displays accurately.
$upDatehour = date("H", strtotime($row2[post_date]));
// trying simple subtraction
$hour = $currentDateHour - upDatehour;
// this is where the result is incorrect, what is wrong here? Any method I've tried gives me the same result, with or without strotime.. it's gotta be something simple, always is!
print strtotime($hour);

Answer 1

You can drastically simplify your code. I'd recommend refactoring it to use DateTime and specifically DateTime::diff().
$now = new DateTime();
$post = new DateTime($row2['post_date']);
$interval = $now->diff($post);
echo "Updated " . $interval->h . " hours ago";
Working example: http://3v4l.org/23AL6
Note that this will only show up to 24 hours difference. If you want to show all hours even for a difference of more than 24 hours, you'll need to figure in the days. Something like this:
$hours = $interval->h + ($interval->format("%a") * 24);
echo "Updated $hours hours ago";
Working example: http://3v4l.org/ilItU

Answer 2

If you are just trying to get the number of hours between two arbitrary times, the easiest way would be to get the difference in seconds of the two times, and then divide by 3600 to determine the number of hours between the two dates.
Here is a basic example:
<?php
$row2['post_date'] = '2013-12-02 07:45:38'; // date from database
$now = time(); // get current timestamp in seconds
$upDate = strtotime($row2['post_date']); // convert date string to timestamp
$diff = $now - $upDate; // subtract difference between the two times
$hours = floor($diff / 3600); // get the number of hours passed between the 2 times
echo $hours; // display result
Also, Wordpress has a built in function that may end up doing what your ultimate goal is, see wordpress function human_time_diff().
Example:
<?php echo human_time_diff( get_the_time('U'), current_time('timestamp') ) . ' ago';
Result:
2 days ago.

Answer 3

Example how to get difference between dates in hours:
$diff = date_diff(date_create(), date_create($row2['post_date']));
$hours = $diff->days * 24 + $diff->h;
If you wish to format output number with leading zeros, you can use sprintf() or str_pad() function. Example of sprintf() use for HH:mm format:
echo sprintf('%02d:%02d', $hours, $diff->i);
demo