Code added to this post will calculate date difference in days, months, years format. So using this code you can calculate age by sending birth date as parameter. Or you can calculate difference between today’s date and any date in past.

function get_Age_difference($start_date,$end_date){
list($start_year,$start_month,$start_date) = split('-', $start_date);
list($current_year,$current_month,$current_date) = split('-', $end_date);
$result = '';
/** days of each month **/
for($x=1 ; $x<=12 ; $x++){
$dim[$x] = date('t',mktime(0,0,0,$x,1,date('Y')));
}
/** calculate differences **/
$m = $current_month - $start_month;
$d = $current_date - $start_date;
$y = $current_year - $start_year;
/** if the start day is ahead of the end day **/
if($d < 0) {
$today_day = $current_date + $dim[$current_month];
$today_month = $current_month - 1;
$d = $today_day - $start_date;
$m = $today_month - $start_month;
if(($today_month - $start_month) < 0) {
$today_month += 12;
$today_year = $current_year - 1;
$m = $today_month - $start_month;
$y = $today_year - $start_year;
}
}
/** if start month is ahead of the end month **/
if($m < 0) {
$today_month = $current_month + 12;
$today_year = $current_year - 1;
$m = $today_month - $start_month;
$y = $today_year - $start_year;
}
/** Calculate dates **/
if($y < 0) {
die("Start Date Entered is a Future date than End Date.");
} else {
switch($y) {
case 0 : $result .= ''; break;
case 1 : $result .= $y.($m == 0 && $d == 0 ? ' year old' : ' year'); break;
default : $result .= $y.($m == 0 && $d == 0 ? ' years old' : ' years');
}
switch($m) {
case 0: $result .= ''; break;
case 1: $result .= ($y == 0 && $d == 0 ? $m.' month old' : ($y == 0 && $d != 0 ? $m.' month' : ($y != 0 && $d == 0 ? ' and '.$m.' month old' : ', '.$m.' month'))); break;
default: $result .= ($y == 0 && $d == 0 ? $m.' months old' : ($y == 0 && $d != 0 ? $m.' months' : ($y != 0 && $d == 0 ? ' and '.$m.' months old' : ', '.$m.' months'))); break;
}
switch($d) {
case 0: $result .= ($m == 0 && $y == 0 ? 'Today' : ''); break;
case 1: $result .= ($m == 0 && $y == 0 ? $d.' day old' : ($y != 0 || $m != 0 ? ' and '.$d.' day old' : '')); break;
default: $result .= ($m == 0 && $y == 0 ? $d.' days old' : ($y != 0 || $m != 0 ? ' and '.$d.' days old' : ''));
}
}
return $result;
}
/* Call this function as */
$date_difference= get_Age_difference("2004-10-10",date("Y-m-d")); /* get_Age_difference(Birthdate,Todays_date) */
echo $date_difference;
Above code will output difference in format like
5 years, 10 months and 13 days old