PHP date function example: get the last day of the month

/**
* Date-get the last day of the month
* @return int
*/
public function get_lastday() {
 if($this->month==2) {
 $lastday = $this->is_leapyear($this-> year) ? 29 : 28;
 } elseif($this->month==4 || $this->month==6 || $this->month==9 || $this->month ==11) {
 $lastday = 30;
 } else {
 $lastday = 31;
 }
 return $lastday;
}

/**
* php date - whether it is a leap year
* @return int
*/
public function is_leapyear($year) {
 return date('L', $year);
}

Example, PHP date function to calculate the difference between two dates

/**
* php date-calculate the difference between 2 dates
* @return int
*/
public function get_difference($date, $new_date) {
 $date = strtotime($date);
 $new_date = strtotime($new_date);
 return abs( ceil(($date - $new_date)/86400));
}