weekday_diff - calculates the number of weekdays between two dates.

weekday_diff.php

<?php
  /**
   * Calculated the number of weekdays (M-F) between two timestamps (inclusive).
   *
   * @param string $from the timestamp to start measuring from
   * @param string $to the timestamp to stop measuring at
   * @param string $normalise whether the time of day should be ignored (forces times to yyyy-mm-ddT00:00:00+00:00)
   * @return int the number of weekdays between the two timestamps
   * @author Matt Harris
   */
  function weekday_diff($from, $to, $normalise=true) {
    $_from = is_int($from) ? $from : strtotime($from);
    $_to   = is_int($to) ? $to : strtotime($to);

    // normalising means partial days are counted as a complete day.
    if ($normalise) {
      $_from = strtotime(date('Y-m-d', $_from));
      $_to = strtotime(date('Y-m-d', $_to));
    }

    $all_days = @range($_from, $_to, 60*60*24);

    if (empty($all_days)) return 0;

    $week_days = array_filter(
      $all_days,
      create_function('$t', '$d = date("w", strtotime("+{$t} seconds", 0)); return !in_array($d, array(0,6));')
    );

    return count($week_days);
  }
?>

Hey! Thanks for the share, but running this like weekday_diff("2018-09-13", "2018-09-13") gives me a result of 1 instead of the expected 0 -- did I misunderstand the purpose/logic or am I running it wrong somehow?