Move an array element to a new index in PHP

Question

I\'m looking for a simple function to move an array element to a new position in the array and resequence the indexes so that there are no gaps in the sequence. It doesnt ne

Answer 1

You need to create an auxiliary variable.

moveElement($a, $i,$j)
  {
  $k=$a[$i];
  $a[$i]=$a[$j];
  $a[$j]=$k;
  return $a;
  }

Answer 2

Arrays in PHP are not actual array in the C sens but associative arrays. But the way to move a value from an index to another is quiet straight forward and is the same as in C++:

Copy the value to move to a temporary buffer, translate all the elements to crush the empty spot at the source position and in the same free up a spot on the destination position. Put the backup value in the destination spot.

function moveElement ($a , $i , $j)
{
      $tmp =  $a[$i];
      if ($i > $j)
      {
           for ($k = $i; $k > $j; $k--) {
                $a[$k] = $a[$k-1]; 
           }        
      }
      else
      { 
           for ($k = $i; $k < $j; $k++) {
                $a[$k] = $a[$k+1];
           }
      }
      $a[$j] = $tmp;
      return $a;
}


$a = array(0, 1, 2, 3, 4, 5);
print_r($a);

$a = moveElement($a, 1, 4);
echo ('1 ->  4');
print_r($a);


$a = moveElement($a, 5, 0);
echo ('5 ->  0' );
print_r($a);

Output:

Array
(
    [0] => 0
    [1] => 1
    [2] => 2
    [3] => 3
    [4] => 4
    [5] => 5
)
1 ->  4Array
(
    [0] => 0
    [1] => 2
    [2] => 3
    [3] => 4
    [4] => 1
    [5] => 5
)
5 ->  0Array
(
    [0] => 5
    [1] => 0
    [2] => 2
    [3] => 3
    [4] => 4
    [5] => 1
)

You'll need to add some Exception handling to have a complete code.

Answer 3

Based on a previous answer. In case if you need to save key indexes of an associative array, which are could be any number or string:

function custom_splice(&$ar, $a, $b){
    $out = array_splice($ar, $a, 1);
    array_splice($ar, $b, 0, $out);
}

function moveElement(&$array, $a, $b) {
    $keys = array_keys($array);

    custom_splice($array, $a, $b);
    custom_splice($keys, $a, $b); 

    $array = array_combine($keys,$array);
}

$s = '{ 
"21": "b", 
"2": "2", 
"3": "3", 
"4": "4", 
"6": "5", 
"7": "6" 
}';
$e = json_decode($s,true);

moveElement($e, 2, 0); 

print_r($e);

Array
(
    [3] => 3
    [21] => b
    [2] => 2
    [4] => 4
    [6] => 5
    [7] => 6
)

Demo

A previous answer destroys numeric indexes - makes them start from 0.