[php+mysql] get working days between dates

[Costas]

the table

CREATE TABLE user_vacations (
  user_vacation_id int(11) NOT NULL AUTO_INCREMENT,
  user_id int(11) DEFAULT NULL,
  date_start date DEFAULT NULL,
  date_end date DEFAULT NULL,
  authorized tinyint(4) DEFAULT NULL,
  comment varchar(200) COLLATE utf8_unicode_ci DEFAULT NULL,
  PRIMARY KEY (user_vacation_id)
) ENGINE=MyISAM AUTO_INCREMENT=11 DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci;

-- ----------------------------
-- Records of user_vacations
-- ----------------------------
INSERT INTO user_vacations VALUES ('1', '3', '2014-10-25', '2014-10-26', '0', '123');
INSERT INTO user_vacations VALUES ('2', '3', '2014-10-16', '2014-10-17', '1', '123');
INSERT INTO user_vacations VALUES ('8', '3', '2014-10-31', '2014-11-09', '0', 'x');
INSERT INTO user_vacations VALUES ('9', '3', '2014-10-20', '2014-10-21', '1', 'x23');
INSERT INTO user_vacations VALUES ('7', '1', '2014-10-17', '2014-10-17', '0', '879');
INSERT INTO user_vacations VALUES ('10', '1', '2014-10-31', '2014-11-11', '1', 'sadfs');

the code

$sql = "select DATE_FORMAT(date_start,'%Y-%m-%d') as date_start,DATE_FORMAT(date_end,'%Y-%m-%d') as date_end interval from user_vacations where date_start is not null and date_end is not null";

foreach($rows as $row) {
	echo $row['date_start'] . ", ".$row['date_end'].'#'.getWorkingDays($row['date_start'],$row['date_end'])."<br>";
}

//cut-down version of 
//http://mugurel.sumanariu.ro/php-2/php-how-to-calculate-number-of-work-days-between-2-dates/
function getWorkingDays($startDate, $endDate)	{
	$begin   = strtotime($startDate);
	$end     = strtotime($endDate);

	$no_days = 0;

	while($begin < $end) {
		$what_day = date("N",$begin);

		if($what_day < 6) // 6 and 7 are weekend days
			$no_days++;

		$begin += 86400; // +1 day
	};

	return $no_days;
}

the result

where with natural SQL query :

SELECT DATE_FORMAT(date_start,'%Y-%m-%d') as date_start,DATE_FORMAT(date_end,'%Y-%m-%d') as date_end,datediff(date_end,date_start) as diff FROM user_vacations