Question

I have an array like:

$arr[0] = ("1-3-2011","1","15"); //date(dd-mm-yyyy),id,amt
$arr[1] = ("1-4-2011","2","5");
$arr[2] = ("12-3-2011","6","20");
$arr[3] = ("1-3-2011","10","10");
$arr[4] = ("12-3-2011","3","10");
$arr[5] = ("1-4-2011","5","15");
$arr[6] = ("1-3-2011","7","15");

From this I need to generate a condensed array like

$newarr[0] = ("1-3-2011","1,7,10","40"); 
$newarr[0] = ("1-4-2011","2,5","20");
..
...

Basically the first one is a multidimentional array, containing date,id, and amount. In the new array, I need to condense the previous one for each unique date, ids as a csv string for duplicate dates, and amounts added.

What’s the most efficient way to do this, performance wise?

Answer 1

Something like this should do it:

$newarr = array();

foreach($arr as $row) {
    if(!isset($newarr[$row[0]])) {
        $newarr[$row[0]] = array('ids' => array(), 'amount' => 0);
    }
    $newarr[$row[0]]['ids'][] = $row[1];
    $newarr[$row[0]]['amount'] += $row[2];
}

foreach($newarr as $key => &$row) {
    $row = array($key, implode(',', $row['ids']), $row['amount']);
} unset($row);

Working example:

http://codepad.org/UmiDKLYJ