How to build unlimited level of menu through PHP and mysql

Question

Well, to build my menu my menu I use a db similar structure like this

  2  Services                  0
  3  Photo Gallery             0
  4  Home                         


        

Answer 1

alt text http://i.imagehost.org/0934/product_hier.jpg http://pastie.org/969286

drop table if exists product;

create table product
(
prod_id smallint unsigned not null auto_increment primary key,
name varchar(255) not null,
parent_id smallint unsigned null,
key (parent_id)
)engine = innodb;


insert into product (name, parent_id) values
('Products',null), 
   ('Systems & Bundles',1), 
   ('Components',1), 
      ('Processors',3), 
      ('Motherboards',3), 
        ('AMD',5), 
        ('Intel',5), 
           ('Intel LGA1366',7);


delimiter ;

drop procedure if exists product_hier;

delimiter #

create procedure product_hier
(
in p_prod_id smallint unsigned
)
begin

declare v_done tinyint unsigned default 0;
declare v_depth smallint unsigned default 0;

create temporary table hier(
 parent_id smallint unsigned, 
 prod_id smallint unsigned, 
 depth smallint unsigned default 0
)engine = memory;

insert into hier select parent_id, prod_id, v_depth from product where prod_id = p_prod_id;

/* http://dev.mysql.com/doc/refman/5.0/en/temporary-table-problems.html */

create temporary table tmp engine=memory select * from hier;

while not v_done do

    if exists( select 1 from product p inner join hier on p.parent_id = hier.prod_id and hier.depth = v_depth) then

        insert into hier 
            select p.parent_id, p.prod_id,  v_depth + 1 from product p 
            inner join tmp on p.parent_id = tmp.prod_id and tmp.depth = v_depth;

        set v_depth = v_depth + 1;          

        truncate table tmp;
        insert into tmp select * from hier where depth = v_depth;

    else
        set v_done = 1;
    end if;

end while;

select 
 p.prod_id,
 p.name as prod_name,
 b.prod_id as parent_prod_id,
 b.name as parent_prod_name,
 hier.depth
from 
 hier
inner join product p on hier.prod_id = p.prod_id
inner join product b on hier.parent_id = b.prod_id
order by
 hier.depth, hier.prod_id;

drop temporary table if exists hier;
drop temporary table if exists tmp;

end #

delimiter ;


call product_hier(3);

call product_hier(5);

Answer 2

http://pastebin.com/ariBn3pE

You need to use recursion, but my approach it's different, I created a class to handle each menu individually, then queried for results and group each elements in their individual object according to their parents, organized that by levels, and then merge all the objects into one... check the pastebin for the full code

Answer 3

I found this way, working with Yii Framework.

$children = array();

foreach($model as $k => $item){
    if(empty($item->cn_id_menu_padre))
        $children[$item->cn_id] = $item->attributes;
    else
        $children[$item->cn_id_menu_padre]['hijos'][] = $item->attributes;
}

foreach($children as $k=>$child){
    if(array_key_exists('hijos',$child))
    {
        echo 'li y dentro ul<br>';
        foreach($child['hijos'] as $hijo){
            echo 'li<br>';
        }
    }
    else
        echo 'li<br>';
}

In case that you need one more level, you could make another level in children array like hijos_de_hijos and do the comparison then in the if statement.

Oh, of course, to compare if cn_id_menu_padre is empty, the value in the database should be null.

Answer 4

i would use a recursive function.

i know this isn't exactly like your code, but I think you can get the general concept if you understand recursion. if you don't understand recursion check out http://en.wikipedia.org/wiki/Recursion_(computer_science)

$list = new List();

function print_menu($list) {

    echo '<ul>';
    foreach($list as $item) {
        echo '<li><a href="#">' . $item->name . '</a>';
        if($item->has_child) {
            print_menu($item);
        }
        echo '</li>';
    }
    echo '</ul>';
}

Answer 5

You need to use recursive functions for this. Technically, there's a few ways to do it, but recursion is really the best option here.

Here's the basic gist of how it would work:

function drawMenu ($listOfItems) {
    echo "<ul>";
    foreach ($listOfItems as $item) {
        echo "<li>" . $item->name;
        if ($item->hasChildren()) {
            drawMenu($item->getChildren()); // here is the recursion
        }
        echo "</li>";
    }
    echo "</ul>";
}

The properties and methods of $item are just examples, and I'll leave it up to you to implement these however you need to, but I think it gets the message across.

Answer 6

Here is a "developer-friendly" version of the "one query, no recursion" solution for this problem.

SQL:

SELECT id, parent_id, title, link, position FROM menu_item ORDER BY parent_id, position;

PHP:

$html = '';
$parent = 0;
$parent_stack = array();

// $items contains the results of the SQL query
$children = array();
foreach ( $items as $item )
    $children[$item['parent_id']][] = $item;

while ( ( $option = each( $children[$parent] ) ) || ( $parent > 0 ) )
{
    if ( !empty( $option ) )
    {
        // 1) The item contains children:
        // store current parent in the stack, and update current parent
        if ( !empty( $children[$option['value']['id']] ) )
        {
            $html .= '<li>' . $option['value']['title'] . '</li>';
            $html .= '<ul>'; 
            array_push( $parent_stack, $parent );
            $parent = $option['value']['id'];
        }
        // 2) The item does not contain children
        else
            $html .= '<li>' . $option['value']['title'] . '</li>';
    }
    // 3) Current parent has no more children:
    // jump back to the previous menu level
    else
    {
        $html .= '</ul>';
        $parent = array_pop( $parent_stack );
    }
}

// At this point, the HTML is already built
echo $html;

You just need to understand the usage of the $parent_stack variable.

It is a "LIFO" stack (Last In, First Out) - the image in the Wikipedia article worths a thousand words: http://en.wikipedia.org/wiki/LIFO_%28computing%29

When a menu option has sub-options, we store its parent ID in the stack:

array_push( $parent_stack, $parent );

And then, we immediately update $parent, making it be the current menu option ID:

$parent = $option['value']['id'];

After we looped all its sub-options, we can return back to the previous level:

$parent = array_pop( $parent_stack );

This is why we stored the parent ID in the stack!

My suggestion is: contemplate the code snippet above, and understand it.

Questions are welcome!

One of the advantages I see in this approach is that it eliminates the risk of entering into an infinite loop, which can happen when recursion is used.