如何按一列對子數組進行分組並從另一列產生逗號分隔值？

$array = [
    ["444", "0081"],
    ["449", "0081"],
    ["451", "0081"],
    ["455", "2100"],
    ["469", "2100"]
];

array (
  0 => 
  array (
    0 => '444,449,451',
    1 => '0081',
  ),
  1 => 
  array (
    0 => '455,469',
    1 => '2100',
  ),
)

<code class="php">$data = []; 
$groups = [];

foreach($data as $item){
    if(!array_key_exists($item[1], $groups)){
        $groups[$item[1]] = [];
    }
    $groups[$item[1]][] = $item[0];
}

$structured = [];
foreach($groups as $group => $values){
    $structured[] = [implode(',', $values), $group];
}</code>