PHP: Last and First day of actual month

last_and_first_month_day.php

  /** Actual month last day **/
  function _data_last_month_day() { 
      $month = date('m');
      $year = date('Y');
      $day = date("d", mktime(0,0,0, $month+1, 0, $year));

      return date('Y-m-d', mktime(0,0,0, $month, $day, $year));
  };

  /** Actual month first day **/
  function _data_first_month_day() {
      $month = date('m');
      $year = date('Y');
      return date('Y-m-d', mktime(0,0,0, $month, 1, $year));
  }