php二维数组如何利用循环遍历转一维数组

$twoDimensionalArray = array(
    array("apple", "banana", "orange"),
    array("car", "bike", "motorcycle"),
    array("sun", "moon", "stars")
);
$oneDimensionalArray = array();
foreach ($twoDimensionalArray as $array) {
    foreach ($array as $element) {
        $oneDimensionalArray[] = $element;
    }
}
print_r($oneDimensionalArray);