Efficient way to sort an array?

Question

I have an array of variabel length, containing events sorted by startdate, looking like this:

Array
(
[0] => stdClass Object
    (
        [id] => 1978
        [date] => 2012-09-29
    )

[1] => stdClass Object
    (
        [id] => 1979
        [date] => 2012-10-14
    )

...etc....

I need to make a function that takes one of the event, and puts in the middle of a new array with a length of exactly seven, and puts the event's neighbours on each side.

So if event 5 passed to the function, the output should be:

[2][3][4][5][6][7][8]

If the first event is passed to the function, and the original amount of events is 12, the output should be:

[10][11][12][1][2][3][4]

If the orignal amount of events is 6, and the fifth event is passed, the output should be:

[2][3][4][5][6][1][]

So the list of events should always "wrap around" in the new array and fill it up as much as possible.

I have hacked together a solution, that involves quite a bit of steps. I dont really like it, and it got me wondering:

How would this be done in the most efficient and elegant way?

What's your current solution? What is your problem in using ksort() or usort()? — Praveen Kumar Purushothaman
– Praveen Kumar Purushothaman, Commented Jan 25, 2013 at 9:21
I have calculated how much the original array will be shifted to either the left or right, and what keys will be "cut off" from the shift. Then I create a new array and start filling it from [3] and then I add the cut off keys to either the left or the right side. It's quite handcoded and leaves me with the feeling, that I should be doing it some other way... — acrmuui
– acrmuui, Commented Jan 25, 2013 at 9:34

Prasanth Bendra · Accepted Answer · 2013-01-25 11:02:28Z

1

You need to change the values in this codes
  define('TO_SHOW',7); // number of items to show in your case it is 7
  $selected      = 1; //// which one you need need at center.

and your array;

Execute this and try :

<?php 

define('TO_SHOW',7); // number of items to show in your case it is 7

function change_order($arry, $sel){
   $arr_cnt      = count($arry);   
   $shift_count  = $arr_cnt - (ceil(TO_SHOW/2)-$sel);
   for($i=0; $i<$shift_count; $i++){
      array_push($arry, array_shift($arry));
   }
   return array_slice($arry, 0, TO_SHOW);
} 

$arr            = array(array(
                    "id" => 1,
                    "date" => 2012-09-29
                    ),
                    array(
                    "id" => 2,
                    "date" => 2012-09-29
                    ),
                    array(
                    "id" => 3,
                    "date" => 2012-09-29
                    ),
                    array(
                    "id" => 4,
                    "date" => 2012-09-29
                    ),
                    array(
                    "id" => 5,
                    "date" => 2012-09-29
                    ),
                    array(
                    "id" => 6,
                    "date" => 2012-09-29
                    ),
                    array(
                    "id" => 7,
                    "date" => 2012-09-29
                    ),
                    array(
                    "id" => 8,
                    "date" => 2012-09-29
                    ),
                    array(
                    "id" => 9,
                    "date" => 2012-09-29
                    ),
                    array(
                    "id" => 10,
                    "date" => 2012-09-29
                    ),
                    array(
                    "id" => 11,
                    "date" => 2012-09-29
                    ),
                    array(
                    "id" => 12,
                    "date" => 2012-09-29
                    ),
                    array(
                    "id" => 13,
                    "date" => 2012-09-29
                    ),
                    array(
                    "id" => 14,
                    "date" => 2012-09-29
                    )
                );

$selected      = 1; //// centre one             
$test   = change_order($arr, $selected);

echo "<pre>";
print_r($test);
?>

edited Jan 25, 2013 at 11:02

answered Jan 25, 2013 at 10:57

Prasanth Bendra

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7 Comments

cmbuckley Over a year ago

Why is $selected an argument for the function, but TO_SHOW is a constant?

Prasanth Bendra Over a year ago

Your selected will be a variable rite? The one which you need in the center

cmbuckley Over a year ago

Yes; but why is TO_SHOW not a variable as well? Seems like unnecessary global scope.

Prasanth Bendra Over a year ago

That will be a constant, how many items you want to show, in question it is 7 in all the cases.

cmbuckley Over a year ago

Still, it's much better to have it as an argument to the function, not something that's global to the entire application.

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