สวัสดีครับ ผมจะรวมข้อมูล Array เข้ารวมกันด้วย PHP ต้องทำยังไง

$array = [
    ['Domain' => '111111x'],
    ['Domain' => '222222x'],
    ['Domain' => '333333x'],
    ['Domain' => '444444x'],
];

$newArray = [];

var_dump($array);
var_dump($newArray);


function getDomain($item, $key)
{
    global $newArray;
    $item = array_change_key_case($item);
    if (array_key_exists('domain', $item)) {
        array_push($newArray, $item['domain']);
    }
}
var_dump(array_walk($array, 'getDomain'));
var_dump($newArray);

		$array = array(
			array('Domain' => '111111x'),
			array('Domain' => '222222x'),
			array('Domain' => '333333x'),
			array('Domain' => '444444x')
		);
		$string = array();
		foreach ($array as $key)
		{
			$string[] = $key['Domain'];
		}
		$new_array = array(
			array('Domain' => join(' ', $string))
		);
		print_r($new_array);