Moving up/down an item in the array by its value

Question

I cannot find an effective solution on rearranging/swapping an array item by its value by shifting by - 1 or + 1. I\'m making an order on tables, i

Answer 1

$ret = array();
for ($i = 0; $i < count($array); $i++) {
    if ($array[$i] == $desired_item_to_move && $i > 0) {
        $tmp = array_pop($ret);
        $ret[] = $array[$i];
        $ret[] = $tmp;
    } else {
        $ret[] = $array[$i];
    }
}

This will move up all instances of the desired element, putting the new array into $ret.

Answer 2

Shifting up (assuming you've checked that the item is not already the first one):

$item = $array[ $index ];
$array[ $index ] = $array[ $index - 1 ];
$array[ $index - 1 ] = $item;

Shifting down:

$item = $array[ $index ];
$array[ $index ] = $array[ $index + 1 ];
$array[ $index + 1 ] = $item;

Answer 3

A useful function for the more general problem of moving an element of an array from one position to another:

function array_move(&$a, $oldpos, $newpos) {
    if ($oldpos==$newpos) {return;}
    array_splice($a,max($newpos,0),0,array_splice($a,max($oldpos,0),1));
}

This can then be used to solve the specific problem in the original question:

// shift up
array_move($array,$index,$index+1);
// shift down
array_move($array,$index,$index-1);

Note, there's no need to check whether or not you're already at the start/end of the array. Note also, this function does not preserve the array keys - moving elements while preserving keys is more fiddly.