PHP は無限分類を再帰的に実装します

$datasection = array(

    array('id' => 1, 'name' => '安徽', 'pid' => 0),
    array('id' => 2, 'name' => '北京', 'pid' => 0),
    array('id' => 3, 'name' => '海淀', 'pid' => 2),
    array('id' => 4, 'name' => '中关村', 'pid' => 3),
    array('id' => 5, 'name' => '合肥', 'pid' => 1),
    array('id' => 6, 'name' => '上地', 'pid' => 3),
    array('id' => 7, 'name' => '河北', 'pid' => 0),
    array('id' => 8, 'name' => '石家庄', 'pid' => 7),
    
    );

function getTree($data, $pId)
{
	$tree = '';
	foreach($data as $k => $v)
	{
		if($v['pid'] == $pId)
		{
			$v['pid'] = getTree($data, $v['id']);
			$tree[] = $v;
			unset($data[$k]);
		}
	}
	return $tree;
}

$tree = getTree($datasection, 0);
print_r($tree);