Move array item with certain key to the first posi

Question

What's the most elegant way in PHP to move an array element chosen by key to the first position?

Input:

$arr[0]=0;
$arr[1]=1;
$arr[2]=2;
....
$arr[n]=n;
$key=10;

Output:

$arr[0]=10;
$arr[1]=0;
$arr[2]=1;
$arr[3]=2;
....
$arr[n]=n;

Answer 1

Use array_unshift:

$new_value = $arr[n];
unset($arr[n]);
array_unshift($arr, $new_value);

Answer 2

Old question, and already answered, but if you have an associative array you can use array_merge.

$arr = array_merge([$key=>$arr[$key]], $arr);

---

EDITED (above to show PHP7+ notation, below is example)

$arr = ["a"=>"a", "b"=>"b", "c"=>"c", "d"=>"d"];
$arr = array_merge(["c"=>$arr["c"]], $arr);

The effective outcome of this operation

$arr == ["c"=>"c", "a"=>"a", "b"=>"b", "d"=>"d"]

Answer 3

Since any numeric key would be re-indexed with array_unshift (as noted in the doc), it's better to use the + array union operator to move an item with a certain key at the first position of an array:

$item = $arr[$key];
unset($arr[$key]);
$arr = array($key => $item) + $arr;

Answer 4

No need to unset keys. To keep it short just do as follow

//appending $new in our array 
array_unshift($arr, $new);
//now make it unique.
$final = array_unique($arr);

Demo

Answer 5

$arr[0]=0;
$arr[1]=1;
$arr[2]=2;
$arr[3]=10;


$tgt = 10;
$key = array_search($tgt, $arr);
unset($arr[$key]);
array_unshift($arr, $tgt);

// var_dump( $arr );
array
0 => int 10
1 => int 0
2 => int 1
3 => int 2

Answer 6

Something like this should work. Check if the array key exists, get its value, then unset it, then use array_unshift to create the item again and place it at the beginning.

if(in_array($key, $arr)) {
    $value = $arr[$key];
    unset($arr[$key]);
    array_unshift($arr, $value);
}