PHP calculate person's current age

Question

I have birth dates on my site in format 12.01.1980.

$person_date (string) = Day.Month.Year

Want to add an oldness of the perso

Answer 1

An extension of @VolkerK's answer - which is excellent! I never like seeing the age of zero, which happens if you only use the year. This function shows their age in months (if they are one month old or more), and otherwise in days.

function calculate_age($birthday)
{
    $today = new DateTime();
    $diff = $today->diff(new DateTime($birthday));

    if ($diff->y)
    {
        return $diff->y . ' years';
    }
    elseif ($diff->m)
    {
        return $diff->m . ' months';
    }
    else
    {
        return $diff->d . ' days';
    }
}