数组层级缩进转换

/**
 * 数组层级缩进转换
 * @param array $array 源数组
 * @param int   $pid
 * @param int   $level
 * @return array
 */
function array2level($array, $pid = 0, $level = 1)
{
    static $list = [];
    foreach ($array as $v) {
        if ($v['pid'] == $pid) {
            $v['level'] = $level;
            $list[]     = $v;
            array2level($array, $v['id'], $level + 1);
        }
    }

    return $list;
}