Get the number of days since a specific date or timestamp in PHP with timezone support.

get_days_since.php

<?php
  
  $date_in_the_past = '@1613681176'; // If using timestamps be sure to include '@' symbol
  $date_in_the_past_obj = new DateTime($date_in_the_past);
  
  // If timezones matter for your usecase, then use below instead. Ref: https://www.php.net/manual/en/timezones.php
  // $date_to_check = '2021-02-18'; 
  // $date_to_check_obj = new DateTime($date_to_check, new DateTimeZone('America/St_Lucia'));
  
  // You can add a different date that you want to compare instead of "today"
  $date_in_the_future = new DateTime('today');

  $date_difference = $date_in_the_past_obj->diff($date_in_the_future);

  $days_since = (int) $date_difference->format('%a');

  echo $days_since;