Question

I am new to taking an object oriented approach with php…actually I have a lot of learning to do overall, but the only way to learn is by doing.

So I have an array that holds several DateTime objects..I know this to be true because I have ran var_dump on the array and it indeed is holding several objects.

I need to go through each date and make sure there is never a difference greater than one day.

My research would seem to indicate that we cannot access or modify an object using the subscript operator:

$foo = $neat_array[$i+1]->format('U') ; //looking to format DateTime object as unix

//this returns an error every time

Okay I am fine with that, but I simply cannot figure out the syntax to access a specific item in the array so that it is seen as an object and does not pull an error.

I have pieced together that using -> is how I need to do it, but I never get any useable result.

Here is pseudo code of what I am trying to do

foreach($date_array as $date)
{

    //check to see if the difference between the next date in the array and the current date of the array is greater than one day.

    //I cannot use diff because I am on php 5.2 so I am trying this

    $date->format('U') and then doing the math

}

Answer 1

Since learning by experimenting (and failing) is IMO a great way to learn, here is something to get you started.

$date_array = array(
  new DateTime("tomorrow"),
  new DateTime("now"),
  new DateTime("yesterday"),
  new DateTime("last day of october")
);

for( $i = 0, $count = count( $date_array); $i < $count; $i += 2) {
  // Get the current object AND the next one in the array
  echo $date_array[ $i ]->format('U'); echo '<br />';
  echo $date_array[ $i + 1 ]->format('U'); echo '<br />';
  // Now that you have the UNIX timestamps, you can do the math you need in here.
}

Note that the above will fail if the array contains an odd number of elements – I’ll leave that fix up to you (if you need it).

Demo

Edit: You’re probably getting that error for one of two reasons:

1. You’re referencing an element that either isn’t a DateTime object
2. You’re referencing an element that doesn’t exist in the date array

Here is a demo that shows error #2.

Edit: Here is a working example based off your answer that works for even and odd array sizes. It is essentially the same, except I don’t bother with saving the values to variables or subtracting and comparing to 1 (since it’s unnecessary).

$session_dates = $date_array = array(
  new DateTime("tomorrow"),
  new DateTime("yesterday"),
  new DateTime("now"),
);

for( $i = 0, $count = count( $date_array) - 1; $i < $count; $i++) 
{
  if(  ($date_array[ $i + 1 ]->format('U') - $date_array[ $i ]->format('U')) > 86400) 
  {
     die( 'The date array does not contain consecutive dates.');
  }
}

See it in action.