PHP DateTime Subtraction and Conversion

Question

It's hard to articulate the problem I'm having in the title, but here's the scenario: I'm working the backend of a 3-tiered exam taking website. I'm currently updating my function used for when students request an exam. The exam has start and end dates and times, as well as a time limit. What I want to do is specific to the case when the amount of time left in the exam period is less than the time limit for the exam, For example, the exam period ends at 5:00PM. The time is now 4:30PM. The exam time limit is an hour and a half. I want to replace the hour and a half time limit with 30 minutes. To do that, there are 3 dates I need, and I will explain how I get each:

• Timestamp for my function page. When the controller calls my page, after I open the session, I set the default timezone to America/New York (my region). To get the timestamp, I use the code:

  $date = date('Y-m-d H:i:s');

  $currenttime = date('H:i:s', strtotime($date));

• I use a function call to my database to acquire the time limit and the time the exam ends (I also use the dates for other comparisons to check exam availability). The exam end time is stored in resultant array $res[10] and the time limit is in $res[11].

• Assuming the due date for the exam is equal to the date of the timestamp, and it is in the exam period (2 checks I perform before), I want to check if the difference between the current time and the end of the exam is less than the time limit. If the time until the exam ends is less than the time limit, I want to set that amount of time as the new time limit. My front end expects my result in the form HH:mm:ss (php's equivalent is H:i:s). So if there is 30 minutes until the exam ends and the time limit is an hour and a half, I want the new time limit to be 30 minutes (or 00:30:00). My code is currently not working as desired. I am meeting the criteria for the if statement, which is my desired result. When I am converting it to the form H:i:s is where the problem seems to be (I keep getting a result around 19:00:00). Every article I've read suggests to do it this way, but I may be missing something.

  $compareTime = strtotime($res[10]) - strtotime($currenttime);
  
  if(compareTime < strtotime($res[11]){
  
      $timelimit = date('H:i:s', $compareTime);
  
  }else{
  
      $timelimit = $res[11];
  
  }
  

If there is a better way of doing this, I'd be much obliged to know. I'm fairly new to php, and admittedly I realize this may be a strange problem, but that's the way the group decided to go.

Answer 1

Maybe it's because the databse and PHP server are using different timezones. Check it out by printing these variables to see their values.