Calculate the number of days between two dates

Here’s a simple function that calculates the number of days between two dates. 

Here’s a simple function that calculates the number of days between two dates.

<?php
//day's seconds = 86400
function days_between($day_i,$month_i,$year_i,$day_f,$month_f,$year_f){
$days_in_between = (mktime(0,0,0,$month_f,$day_f,$year_f) - mktime(0,0,0,$month_i,$day_i,$year_i))/86400;
return $days_in_between;
}
?>

//If we want to calculate the days between 21/8/2009 and 1/9/2009 then
echo days_between(21,8,2009,1,9,2009);
//would give us 11