[WordPress] Find The Difference in Dates Using PHP (and WordPress)

00-difference-in-dates-in-php.php

<?php

/**
 * Determines the number of years that exist between the specified
 * event custom post type and today's date.
 *
 * @access private
 * @param  WP_Post $event A custom post type representing an event.
 * @return string  $years The difference in years.
 */
private function get_difference_in_dates( $event ) {

  // If the post_date is empty, why are we here?
  if ( empty( $event['post_date'] ) {
    return;
  }
  
  // Get the date for the start of the event and te 
  $start = date( 'n/j/Y', strtotime( $event['post_date'] ) );
  $today = date( 'n/j/Y' );

  // Get the date for the start of the event and today's date.
  $start      = new \DateTime( $start );
  $end        = new \DateTime( $today );
      
  // Now find the difference in years.
  $difference = $start->diff( $end );
  $years      = $difference->y;
  
  // If the difference is less than one, we'll return a string of "< 1".
  $years = ( 1 > $years ) ?
    '< 1' :
    (string)$years;

  return $years;
}