PHP convert date interval diff to decimal - php

Question

I'm trying to convert the difference between two dates into a total year count, right now I'm using this:
$datetime1 = new DateTime('2009-10-11');
$datetime2 = new DateTime('2010-10-10');
$interval = $datetime1->diff($datetime2);
return $interval->format('%y');
This returns me an int (Like 0 for < than a year, 2 for two years, etc.)
I need the result to be decimal as following:
0.9 - 9 months
1.2 - 1 year and two months
3.5 - 3 years and five months
and so on..
Thanks!

Answer 1

If you don't care about perfect accuracy:
return $interval->days / 365;
You could also do something like return $interval->y + $interval->m / 12 + $interval->d / 365.
Didn't even notice your weird decimal convention until I saw #2unco's comment. That would look like: return $interval->y . '.' . $interval->m.

Answer 2

Here you can see a function that does exactly that and with many options:
http://php.net/manual/es/function.date-diff.php#98615
<?php
/*
* A mathematical decimal difference between two informed dates
*
* Author: Sergio Abreu
* Website: http://sites.sitesbr.net
*
* Features:
* Automatic conversion on dates informed as string.
* Possibility of absolute values (always +) or relative (-/+)
*/
function s_datediff( $str_interval, $dt_menor, $dt_maior, $relative=false){
if( is_string( $dt_menor)) $dt_menor = date_create( $dt_menor);
if( is_string( $dt_maior)) $dt_maior = date_create( $dt_maior);
$diff = date_diff( $dt_menor, $dt_maior, ! $relative);
switch( $str_interval){
case "y":
$total = $diff->y + $diff->m / 12 + $diff->d / 365.25; break;
case "m":
$total= $diff->y * 12 + $diff->m + $diff->d/30 + $diff->h / 24;
break;
case "d":
$total = $diff->y * 365.25 + $diff->m * 30 + $diff->d + $diff->h/24 + $diff->i / 60;
break;
case "h":
$total = ($diff->y * 365.25 + $diff->m * 30 + $diff->d) * 24 + $diff->h + $diff->i/60;
break;
case "i":
$total = (($diff->y * 365.25 + $diff->m * 30 + $diff->d) * 24 + $diff->h) * 60 + $diff->i + $diff->s/60;
break;
case "s":
$total = ((($diff->y * 365.25 + $diff->m * 30 + $diff->d) * 24 + $diff->h) * 60 + $diff->i)*60 + $diff->s;
break;
}
if( $diff->invert)
return -1 * $total;
else return $total;
}
/* Enjoy and feedback me ;-) */
?>

Answer 3

Simpler and more accurate interval converter to days/hours/minutes/seconds:
function DateDiffInterval($sDate1, $sDate2, $sUnit='H') {
//subtract $sDate2-$sDate1 and return the difference in $sUnit (Days,Hours,Minutes,Seconds)
$nInterval = strtotime($sDate2) - strtotime($sDate1);
if ($sUnit=='D') { // days
$nInterval = $nInterval/60/60/24;
} else if ($sUnit=='H') { // hours
$nInterval = $nInterval/60/60;
} else if ($sUnit=='M') { // minutes
$nInterval = $nInterval/60;
} else if ($sUnit=='S') { // seconds
}
return $nInterval;
} //DateDiffInterval