In PHP, how do you change the key of an array element?

Question

I have an associative array in the form key => value where key is a numerical value, however it is not a sequential numerical value. The key is actually an I

Answer 1

$array = [
    'old1' => 1
    'old2' => 2
];

$renameMap = [
    'old1' => 'new1',   
    'old2' => 'new2'
];

$array = array_combine(array_map(function($el) use ($renameMap) {
    return $renameMap[$el];
}, array_keys($array)), array_values($array));

/*
$array = [
    'new1' => 1
    'new2' => 2
];
*/

Answer 2

This basic function handles swapping array keys and keeping the array in the original order...

public function keySwap(array $resource, array $keys)
{
    $newResource = [];

    foreach($resource as $k => $r){
        if(array_key_exists($k,$keys)){
            $newResource[$keys[$k]] = $r;
        }else{
            $newResource[$k] = $r;
        }
    }

    return $newResource;
}

You could then loop through and swap all 'a' keys with 'z' for example...

$inputs = [
  0 => ['a'=>'1','b'=>'2'],
  1 => ['a'=>'3','b'=>'4']
]

$keySwap = ['a'=>'z'];

foreach($inputs as $k=>$i){
    $inputs[$k] = $this->keySwap($i,$keySwap);
}

Answer 3

this code will help to change the oldkey to new one

$i = 0;
$keys_array=array("0"=>"one","1"=>"two");

$keys = array_keys($keys_array);

for($i=0;$i<count($keys);$i++) {
    $keys_array[$keys_array[$i]]=$keys_array[$i];
    unset($keys_array[$i]);
}
print_r($keys_array);

display like

$keys_array=array("one"=>"one","two"=>"two");

Answer 4

If you want to replace several keys at once (preserving order):

/**
 * Rename keys of an array
 * @param array $array (asoc)
 * @param array $replacement_keys (indexed)
 * @return array
 */
function rename_keys($array, $replacement_keys)  {
      return array_combine($replacement_keys, array_values($array));
}

Usage:

$myarr = array("a" => 22, "b" => 144, "c" => 43);
$newkeys = array("x","y","z");
print_r(rename_keys($myarr, $newkeys));
//must return: array("x" => 22, "y" => 144, "z" => 43);

Answer 5

You could use a second associative array that maps human readable names to the id's. That would also provide a Many to 1 relationship. Then do something like this:

echo 'Widgets: ' . $data[$humanreadbleMapping['Widgets']];

Answer 6

If you want also the position of the new array key to be the same as the old one you can do this:

function change_array_key( $array, $old_key, $new_key) {
    if(!is_array($array)){ print 'You must enter a array as a haystack!'; exit; }
    if(!array_key_exists($old_key, $array)){
        return $array;
    }

    $key_pos = array_search($old_key, array_keys($array));
    $arr_before = array_slice($array, 0, $key_pos);
    $arr_after = array_slice($array, $key_pos + 1);
    $arr_renamed = array($new_key => $array[$old_key]);

    return $arr_before + $arr_renamed + $arr_after;
}