php树状

$data = [
    ['self' => 'd', 'parent' => 'c'],
    ['self' => 'b', 'parent' => 'a'],
    ['self' => 'c', 'parent' => 'b'],
    ['self' => 'e', 'parent' => 'a'],
    ['self' => 'a', 'parent' => null],
    ['self' => 'f', 'parent' => 'e'],
    ['self' => 'h', 'parent' => 'g'],
    ['self' => 'g', 'parent' => 'f'],
    ['self' => 'h', 'parent' => null],
    ['self' => 'i', 'parent' => 'h'],
    ['self' => 'j', 'parent' => 'g'],
];
/**
 * @param $data 节点
 * @param $parent 父节点
 * @param string $keySelf 标识字符串
 * @param string $keyParent 父节点标识字符串
 * @param string $keyChild 子节点标识字符串
 * @param null $null 空父节点标识字符串
 * @return mixed 节点
 */
function parent($data, $parent, $keySelf = 'self', $keyParent = 'parent', $keyChild = 'child', $null = null)
{
    foreach ($data as $key => $value) {
        if ($value[$keySelf] == $parent[$keyParent]) {//查找到父级
            $data[$key][$keyChild][] = $parent;//子级加入到父级child
            return $data;
        } elseif (isset($value[$keyChild])) {//未查找到父级,节点存在子级
            $data[$key][$keyChild] = parent($value[$keyChild], $parent, $keySelf, $keyParent, $keyChild, $null);//节点的子级中查找父级
        }
    }
    return $data;
}

/**
 * @param $data 节点数组,结构中包括标识(string,唯一,必须),父节点标识(string,非必须),可包含任意其他数据
 * @param string $keySelf 标识字符串
 * @param string $keyParent 父节点标识字符串
 * @param string $keyChild 子节点标识字符串
 * @param null $null 空父节点标识字符串
 * @return mixed 树状数组
 */
function tree($data, $keySelf = 'self', $keyParent = 'parent', $keyChild = 'child', $null = null)
{
    foreach ($data as $key => $value) {
        if ($value[$keyParent] != $null) {//处理非顶级
            $data = parent($data, $value, $keySelf, $keyParent, $keyChild, $null);//查找父级
            unset($data[$key]);
        }
    }
    return $data;
}

var_dump(tree($data));