一维数组变成二维数组(多组合)

function index($array, $key, $groups = [])
{
    $result = [];
    $groups = (array)$groups;

    foreach ($array as $element) {
        $lastArray = &$result;

        foreach ($groups as $group) {
            $value = getValue($element, $group);
            if (!array_key_exists($value, $lastArray)) {
                $lastArray[$value] = [];
            }
            $lastArray = &$lastArray[$value];
        }

        if ($key === null) {
            if (!empty($groups)) {
                $lastArray[] = $element;
            }
        } else {
            $value = getValue($element, $key);
            if ($value !== null) {
                if (is_float($value)) {
                    $value = (string) $value;
                }
                $lastArray[$value] = $element;
            }
        }
        unset($lastArray);
    }

    return $result;
}
function getValue($array, $key, $default = null)
{
    if ($key instanceof \Closure) {
        return $key($array, $default);
    }

    if (is_array($key)) {
        $lastKey = array_pop($key);
        foreach ($key as $keyPart) {
            $array = getValue($array, $keyPart);
        }
        $key = $lastKey;
    }

    if (is_array($array) && (isset($array[$key]) || array_key_exists($key, $array)) ) {
        return $array[$key];
    }

    if (($pos = strrpos($key, '.')) !== false) {
        $array = getValue($array, substr($key, 0, $pos), $default);
        $key = substr($key, $pos + 1);
    }

    if (is_object($array)) {
        // this is expected to fail if the property does not exist, or __get() is not implemented
        // it is not reliably possible to check whether a property is accessable beforehand
        return $array->$key;
    } elseif (is_array($array)) {
        return (isset($array[$key]) || array_key_exists($key, $array)) ? $array[$key] : $default;
    } else {
        return $default;
    }
}
$a = [
    ['id'=>'1111','pform_uid'=>'2222','pform_field_id'=>'3333','value'=>'北京','customer_pform_uid'=>'4444'],
    ['id'=>'aaaa','pform_uid'=>'bbbb','pform_field_id'=>'cccc','value'=>'上海','customer_pform_uid'=>'dddd'],
    ['id'=>'1111','pform_uid'=>'BBBB','pform_field_id'=>'CCCC','value'=>'深圳','customer_pform_uid'=>'DDDD'],
];
$b = index($a, 'id', null);
//$c = index($a,  null, 'id');

var_dump($b);die;
//  array (size=1)
//  4444 =>
//       array (size=1)
//            3333 => string '北京' (length=6)