How do I move an array element with a known key to the end of an array in PHP?

Question

Having a brain freeze over a fairly trivial problem. If I start with an array like this:

$my_array = array(
                  \'monkey\'  => array(...),
          


        

Answer 1

You can implement some basic calculus and get a universal function for moving array element from one position to the other.

For PHP it looks like this:

function magicFunction ($targetArray, $indexFrom, $indexTo) { 
    $targetElement = $targetArray[$indexFrom]; 
    $magicIncrement = ($indexTo - $indexFrom) / abs ($indexTo - $indexFrom); 

    for ($Element = $indexFrom; $Element != $indexTo; $Element += $magicIncrement){ 
        $targetArray[$Element] = $targetArray[$Element + $magicIncrement]; 
    } 

    $targetArray[$indexTo] = $targetElement; 
}

Check out "moving array elements" at "gloommatter" for detailed explanation.

http://www.gloommatter.com/DDesign/programming/moving-any-array-elements-universal-function.html

Answer 2

The only way I can think to do this is to remove it then add it:

$v = $my_array['monkey'];
unset($my_array['monkey']);
$my_array['monkey'] = $v;

Answer 3

Contributing to the accepted reply - for the element not to be inserted into the same position, but to be placed at the end of the array:

$v = $my_array['monkey'];
unset($my_array['monkey']);

instead of:

$my_array['monkey'] = $v;

use:

array_push($my_array, $v);

Answer 4

array_shift is probably less efficient than unsetting the index, but it works:

$my_array = array('monkey' => 1, 'giraffe' => 2, 'lion' => 3);
$my_array['monkey'] = array_shift($my_array);
print_r($my_array);

Another alternative is with a callback and uksort:

uksort($my_array, create_function('$x,$y','return ($y === "monkey") ? -1 : 1;'));

You will want to use a proper lambda if you are using PHP5.3+ or just define the function as a global function regularly.

Answer 5

I really like @Gordon's answer above for it's elegance as a one liner, but it only works if the key is at the beginning. Here's another one liner that will work for a key in any position:

$arr = array('monkey' => 1, 'giraffe' => 2, 'lion' => 3);
$arr += array_splice($arr,array_search('giraffe',array_keys($arr)),1);

EDIT: Beware, this fails with numeric keys.