PHP infinite classification related

Find a direct subset of a certain parent
Database field partial excerpt
id (self-increment) pid (parent ID)

$categorys=Db;;name(表名)->where(筛选条件)->field(查询字段，必须含有id，pid)->select();
//查询所有符合条件的分类（或者是其它满足无限级的数据）

function getChildren($categorys,$id=0){
    
    
	$arr= [];
	foreach($categorys as $item){
    
    
		if($item['pid']==$id)
			$arr[]=$item;
	}
	return $arr;
}

Get all children of a category

function getChildren($categorys,$id=0,$level=1){
    
    
    $subs=array();
    foreach($categorys as $item){
    
    
        if($item['pid']==$id){
    
    
            $item['level']=$level;
            $subs[]=$item;
            $subs=array_merge($subs,getChildren($categorys,$item['id'],$level+1));
            
        }
            
    }
    return $subs;
}