Question

If you have an array of ISO dates, how would you calculate the most days between two sequential dates from the array?

$array = array('2009-03-11', '2009-03-12', '2009-04-12', '2009-05-03', '2009-10-30');

I think I need a loop, some sort of iterating variable and a sort. I can’t quite figure it out.

This is actually being output from MYSQL.

Answer 1

Here is how you can do it in PHP:

<?php
$array = array('2009-03-11', '2009-03-12', '2009-04-12', '2009-05-03', '2009-10-30');

# PHP was throwing errors until I set this
# it may be unnecessary depending on where you
# are using your code:
date_default_timezone_set("GMT");

$max = 0;
if( count($array) > 1 ){
    for($i = 0; $i < count($array) - 1; $i++){
        $start = strtotime( $array[$i] );
        $end   = strtotime( $array[$i + 1] );

        $diff  = $end - $start;
        if($diff > $max) $max = $diff; 
    }
}

$max = $max / (60*60*24);

?>

It loops throw your items (it executes one less time than there are number of items) and compares each one. If the comparison is larger than the next, it updates max. Time is in seconds, so after the loop is over we convert the seconds into days.