Group array objects by closest start and end dates

group_objects_by_date.php

<?php

// function described in greater detail here: 
// http://stackoverflow.com/questions/8492458/whats-the-best-logic-for-grouping-objects-by-closest-start-and-end-dates

function cmp($a, $b){ 
return strcmp($a['start'], $b['start']); 
}

$query = array(array('name' =>'A','start' =>'1/1/2011','end' =>'1/31/2011'),array('name' =>'B','start' =>'1/15/2011','end' =>'1/31/2011'),array('name' =>'C','start' =>'2/1/2011','end' =>'2/28/2011'),array('name' =>'D','start' =>'2/2/2011','end' =>'2/28/2011'),array('name' =>'E','start' =>'1/31/2011','end' =>'3/1/2011'), array('name' =>'F','start' =>'3/3/2011','end' =>'3/31/2011'));

usort($query, "cmp"); // organize by start date

$result = array(); 

$c = count($query);
for($i = 1; $i <= $c; $i++) {
if (empty($result)) {
    $result[0][0] = $query[0];
    unset($query[0]);
    $query = array_values($query);  

} else {

    $lastkey_group = array_pop(array_keys($result)); 
    $lastkey_object = array_pop(array_keys($result[$lastkey_group]));

    // get the last object's end date
    $last_end_date = strtotime($result[$lastkey_group][$lastkey_object]['end']);

    $match_days = 1000;
    $match_key = 1000;

    foreach($query as $key => $q) {
        $this_start_date = strtotime($q['start']);
        $diff = round(($this_start_date - $last_end_date)/86400);
        // compare to start date in each $q
        if($diff < $match_days && $diff > 0) {                     
            // if the distance is greater than 0 but less than $diff, 
            // replace match with distance and row key
            $match_days = $diff;
            $match_key = $key;
        } 
    }


    if($match_key == 1000) {                
        $result[$lastkey_group + 1][0] = $query[0]; // no good matches. write to a new group 
        unset($query[0]);       
        $query = array_values($query);

    } else {
        $result[$lastkey_group][$lastkey_object + 1] = $query[$match_key]; 
            // match. write to this group
        unset($query[$match_key]);
        $query = array_values($query);
    }   
}
}
 var_dump($result);

?>