PHP Day add function

How to add 2 days to a date in PHP?
There are many ways to add days to a string date. The best function is the following one:

function dayadd($days,$date=null , $format="d/m/Y"){
	return date($format,strtotime($days." days",strtotime( $date ? $date : date($format) )));
}

This function let you decide the date to which add the days, the output format and days to add. To use the function look these examples:

echo dayadd(2);  // 2 days after today
echo dayadd(-2,null,"Y-m-d");  // 2 days before today with given format
echo dayadd(3,"12/31/2009");  // 3 days after given date
echo dayadd(3,"12/31/2009","d-m-Y");  // 3 days after given date with given format