Calculate Age from Date with PHP

Calculating the age based on a date is a pretty simple task that can be accomplished many different ways (Google yield’s quite a few different approaches). The caveat that usually arises is that you need to factor in which side of the birthday you are on based on the day’s date. What I mean is, using myself as the example, I was born on February 23rd. From January 1st to the 22nd of 2013 I was 31 years old. From the 23rd of February until February 22nd, 2014 I will be be 32 years old. To accomplish this you will need to determine what date it is and calculate the difference accordingly:

$birthday           = '1981-02-23'
$today              = date('Y-m-d'
list($y1, $m1, $d1) = explode('-', $birthday
list($y2, $m2, $d2) = explode('-', $today
$m1                 = $m2 - $m1

if ($m1 < 0 || ($m1 == 0 && $d2 - $d1 < 0))

$age = $y2 - $y1

Sorry about the abbreviated variable names, generally not my style but thought it was be just as confusing using $dob_year and $today_year. Okay, maybe it wouldn’t have been so bad. The gist is depending if the current date is before or on / after the birthday, offset the year before calculation.

There is a significantly shorter (but not nearly as accurate in my opinion) way to calculate the age:

$age = floor((time() - strtotime($birthday)) / 31556926

The value 31556926 is the equivalent of 365.242190 days, or what we consider to be a full year (factors in leap day and such). Fact is, time is relevant and we could get into a whole debate over the exactly length of a year. This shorter solution will get you the right answer and I’m actually unsure under what scenario it would falter (it would only be for part a day when it does though).

Now these are both great examples if you’re using a PHP version before 5.3 which introduced the date_diff() function which is simply an alias for DateTime::diff() but with significantly reduced syntax. As both were introduced in 5.3, there’s no reason to use the longer syntax (and I won’t be discussing it). To get the age all you need is:

$datetime = date_diff(date_create(), date_create($birthday
$age      = $datetime->format('%Y'

Okay, so it’s a bit longer than the previous example, but it also give you the flexibility to return more than just the year. With the format() object function (or date_format() if you’d rather pass the $datetime object as an argument) you could get how many years, months, days, hours, minutes and seconds old someone is. Could come in handy if you had a website for your child and wanted to calculate how many months old they are for the first year (or 2 as most people seem to do).

Josh Sherman - The Man, The Myth, The Avatar

About Josh

Husband. Father. Pug dad. Musician. Founder of Holiday API, Head of Engineering and Emoji Specialist at Mailshake, and author of the best damn Lorem Ipsum Library for PHP.

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