php类递归层次结构

Question

I have category hierarchy like this.

• 721 parent is 235
• 235 parent is 201
• 201 parent is 1
• 1 parent is 0

0 is the root category id, I am trying to build a function that input leaf id 721, get full path id of 721, 235, 201, 1

public function getPath($inputId = 0, $idList=array())
{       
    $sql ="SELECT * FROM hierarchy where id='{$inputId}'";
    $result = $this->db->fetchAll($sql);

    if($result){
        $currentId = $result[0]["id"];
        $parentId = $result[0]["parent_id"];

        $idList[] = $currentId;

        if ($parentId !=0){
           $this->getPath($parentId, $idList);
        }else{
            //var_dump($idList);
            return $idList;
        }
    }

}

I can see correct results in var_dump part above, but when I use this function from another class, it return null, like this $data = $whateveHelper->getPath('721');

could anyone help?

Thanks

Answer 1

You just need to change this:

if ($parentId !=0){
    $this->getPath($parentId, $idList);
}

to this:

if ($parentId !=0){
    return $this->getPath($parentId, $idList);
}

Then you need to remove the else clause and move the "return $idList;" line to the bottom of your function so it is always returned. Your code above would only return $idList in the event that the $parentId was 0. However, you need the function to always return something if you are calling it recursively.

I recommend something along these lines for your whole function:

public function getPath($inputId = 0, $idList=array())
{       
    $sql ="SELECT * FROM hierarchy where id='{$inputId}'";
    $result = $this->db->fetchAll($sql);

    if($result){
        $currentId = $result[0]["id"];
        $parentId = $result[0]["parent_id"];

        $idList[] = $currentId;

        if ($parentId !=0){
           return $this->getPath($parentId, $idList);
        }
    }
    return $idList;
}

Let me know if that works for you.

Answer 2

The line:

$this->getPath($parentId, $idList);

Needs to be

return $this->getPath($parentId, $idList);