PHP List Hierarchy

[litewarez]

The problem is that most programmers including the better ones will always do recursive calls to the database, causing higher load on the DB.

You can do this in a single pass, using PHP References.

Example:

$refs = array();
$list = array(); //This is the baby

$result = mysql_query("SELECT * FROM releases");

while($data = @mysql_fetch_assoc($result))
{
    //Cfreate / Select a referenced variable in the memory
    $thisref = &$refs[ $data['id'] ];

    //Set the parent id
    $thisref['parent'] = $data['parent'];

    //Set the data as your going to need it later
    $thisref['data'] = $data;

    //If its not a root, set the referenced array
    if ($data['parent'] == 0)
    {
        $list[ $data['id'] ] = &$thisref;
    }
    else
    {
        $refs[ $data['parent'] ]['children'][ $data['id'] ] = &$thisref;
    }
} 

Example of why references works is like so:



The code above will replicate hierarchy in a PHP

[theforumdrunk]

Thanks very much! Wow, i'll take a look at this in a couple days and try to get my head around it.

Can you show an example for grandchildren? I'll perhaps get a better perspective.

EDIT: @dermechove Thanks that worked!

[Whoo]

The problem is that most programmers including the better ones will always do recursive calls to the database, causing higher load on the DB.

Hey,

Yeah litewarez it's true, but still, we are working with someone who is learning PHP and therefor I didn't give him any code that he wouldn't understand .

I have been coding (not part of my job/uni) PHP for many years now and I never even used the '&' sign or anything

Anyways, just had a look at your code, and that would work too.

[SplitIce]

references are really ugly in the over all scheme of things. Usually they can be advoided and in this case it can by loading all the data from the table into an array to begin with and instead of querying the database looking it up in the hash table/array (key=>value).

In reality although your solution has better performance litewarez, Whoo's is better for the skill level of the OP.

[litewarez]

References are not ugly, if i used a custom class for storing the data they would be passed by reference anyways as of PHP5

References allow control over the data in the memory, as your referencing data and not creating new ones.

Yeah litewarez it's true, but still, we are working with someone who is learning PHP and therefor I didn't give him any code that he wouldn't understand .

This is a new technique that should be used as standard, if he is new to PHP, should we not teach him the best possible solution regardless weather its its slightly more demanding for a newbie ?