PHP rename array keys in multidimensional array

foreach ( $array as $k=>$v )
{
  $array[$k] ['id'] = $array[$k] ['fee_id'];
  unset($array[$k]['fee_id']);
}

This should work

$arrayNum = count($theArray);

for( $i = 0 ; $i < $arrayNum ; $i++ )
{
    $fee_id_value = $theArray[$i]['fee_id'];
    unset($theArray[$i]['fee_id']);
    $theArray[$i]['id'] = $fee_id_value;
}

This should work.

Copy the current 'fee_id' value to a new key named 'id' and unset the previous key?

foreach ($array as $arr)
{
  $arr['id'] = $arr['fee_id'];
  unset($arr['fee_id']);
}

There is no function builtin doing such thin afaik.

Multidimentional array key can be changed dynamically by following function:

function change_key(array $arr, $keySetOrCallBack = []) 
{
    $newArr = [];

    foreach ($arr as $k => $v) {

        if (is_callable($keySetOrCallBack)) {
            $key = call_user_func_array($keySetOrCallBack, [$k, $v]);
        } else {
            $key = $keySetOrCallBack[$k] ?? $k;
        }

        $newArr[$key] = is_array($v) ? array_change_key($v, $keySetOrCallBack) : $v;
    }

    return $newArr;
}

Sample Example:

$sampleArray = [
    'hello' => 'world', 
    'nested' => ['hello' => 'John']
];

//Change by difined key set
$outputArray = change_key($sampleArray, ['hello' => 'hi']);
//Output Array: ['hi' => 'world', 'nested' => ['hi' => 'John']];

//Change by callback  
$outputArray = change_key($sampleArray, function($key, $value) {
      return ucwords(key);
});
//Output Array: ['Hello' => 'world', 'Nested' => ['Hello' => 'John']];