function to calculate age

gistfile1.php

<?php 
function how_old_am_i($todaydate, $mybday) {

//convert given dates to timestamps
$currenttimestamp = strtotime($todaydate);
$bdaytimestamp = strtotime($mybday);

//get just the years from the timestamps
$currentyear = date("Y",$currenttimestamp);
$mybd = date ("Y",$bdaytimestamp);

//get the current months as numbers (so they can be compared)
$currentmonth	= date("m", $currenttimestamp);
$birthmonth = date("m", $bdaytimestamp);

//get the current days as numbers
$currentday = date("d",$currenttimestamp );
$birthdate = date("d",$bdaytimestamp );

//if current month is same as birth month AND current day is less than birth day, then age is minus 1
$currentage = ($currentyear - $mybd);

if ($currentmonth == $birthmonth && $currentday < $birthdate) {

	echo 'you are ' . ($currentage - 1) . ' years old';
}
//otherwise it's simply current year minus birth year
else {
	echo 'you are ' . ($currentage) . ' years old';
}


 }

how_old_am_i ('1 January 2015', '27 February 1976' );