如何设计一个带有菜单项的树形菜单？

Question

I have an array like below (in PHP):

$menu = array(0 => array('id'=>1, 'name'=>'a', 'parent_id'=>''), 1 => array('id'=>2, 'name'=>'b', 'parent_id'=>''), 2 => array('id'=>3, 'name'=>'c', 'parent_id'=>'1'), 3 => array('id'=>4, 'name'=>'d', 'parent_id'=>''), 4 => array('id'=>5, 'name'=>'e', 'parent_id'=>''), 5 => array('id'=>6, 'name'=>'f', 'parent_id'=>'4'));

then I want to echo this array to something like this:

a
|-- c
b
d
|-- f
e

and if I push new item to array like this: array_push ($menu, array('id'=>7, 'name'=>'g', 'parent_id'=>'6'));

it should be something like this:

a
|-- c
b
d
|-- f
|-- |-- g
e

do you have any solution for this?
thanks a lot
Reza

Hi again, I post my solution but there is something wrong. if I add something like this array_push ($menu, array('id'=>7, 'name'=>'g', 'parent_id'=>'6')); to my array, it will build above tree without any problem.
but if I add this item to array array_push ($menu, array('id'=>7, 'name'=>'g', 'parent_id'=>'4')); it will hang because of infinity loop.
I don't know why it will not exit from the "while" loop. can you please review my code and tell me what is wrong?
thanks again.
Reza

Answer 1

Try this one out, I guess it's pretty messy...

$menu = array(0 => array('id'=>1, 'name'=>'a', 'parent_id'=>''), 1 => array('id'=>2, 'name'=>'b', 'parent_id'=>''), 2 => array('id'=>3, 'name'=>'c', 'parent_id'=>'1'), 3 => array('id'=>4, 'name'=>'d', 'parent_id'=>''), 4 => array('id'=>5, 'name'=>'e', 'parent_id'=>''), 5 => array('id'=>6, 'name'=>'f', 'parent_id'=>'4'));
array_push ($menu, array('id'=>7, 'name'=>'g', 'parent_id'=>'6'));

$menu_arranged = array();



foreach ($menu as $k=>$v) {         // change array layout
    $id = $v['id'];
    unset($v['id']);
    $menu_arranged[$id] = $v;

}


$i = 0;
while($i < 5) {     // i put 5 as number of subtree levels since i can't find easy way to calculate it
    foreach ($menu_arranged as $k=>$v) {
        $parent = $v['parent_id'];
        if (!empty($parent)) {
            $menu_arranged[$parent][$k] = $menu_arranged[$k];
        }
    }
    $i++;
}

foreach ($menu_arranged as $k => $v) {
    if (!empty($v['parent_id'])) {
        unset($menu_arranged[$k]);
    }
}

echo "<pre>";
print_r($menu_arranged);
echo "</pre>";

Answer 2

    $menu = array(0 => array('id'=>1, 'name'=>'a', 'parent_id'=>''), 1 => array('id'=>2, 'name'=>'b', 'parent_id'=>''), 2 => array('id'=>3, 'name'=>'c', 'parent_id'=>'1'), 3 => array('id'=>4, 'name'=>'d', 'parent_id'=>''), 4 => array('id'=>5, 'name'=>'e', 'parent_id'=>''), 5 => array('id'=>6, 'name'=>'f', 'parent_id'=>'4'));
    array_push ($menu, array('id'=>7, 'name'=>'g', 'parent_id'=>'6'));

    public function sort_array_by_levels ($array)
 {
    $new = array();
    $i = 0;
    $sub_level = 1;
    $search_for_next_root = FALSE;
    $temp = array();
    $root_items_holder = array();

    while (count($array) > 0)
    {
        $set_i_to_zero = FALSE;
        //select first item without parent
        if (! $search_for_next_root)
        {
            foreach ($array as $key => $value)
            {
                if ($value['parent_id'] == 0 || $value['parent_id'] === 0 || $value['parent_id'] == '0')
                {
                    array_push($new, $array[$key]);
                    array_push($root_items_holder, $array[$key]);

                    $temp = $array[$key];
                    unset($array[$key]);
                    $array = array_values($array);
                    $search_for_next_root = TRUE;
                    $i = 0;
                    //break to find sub items for this "root item"
                    break;
                }
            }
        }

        //search for sub items
        //if (count($root_items_holder) > 0)
        if ($search_for_next_root)
        {
            //should search for all items in array
            if ($i < count($array))
            {
                if ($array[$i]['parent_id'] == $temp['id'])
                {
                    //next level sub item found
                    for($j=0; $j < $sub_level; $j++)
                    {
                        $array[$i]['name'] = "|-- " . $array[$i]['name'];
                    }

                    array_push($new, $array[$i]);
                    array_push($root_items_holder, $array[$i]);

                    $temp = $array[$i];
                    //set remove sub-item founded and re-index array again
                    unset($array[$i]);
                    $array = array_values($array);
                    //set $i to zero to search from first cell in array
                    $set_i_to_zero = TRUE;
                    $sub_level++;//to add "|-- " as how many as needed to the sub levels
                }
            } else
            {
                //seems that all of array searched and there is no item with last founded item as it's parent,
                //then we should find next "root item" and search for it's sub levels again.
                if (count($root_items_holder) > 0)
                {
                    array_pop($root_items_holder);

                    if (count($root_items_holder) > 0)
                    {
                        $temp = $root_items_holder[(count($root_items_holder)-1)];
                        $sub_level--;
                    } else
                    {
                        $search_for_next_root = FALSE;
                    }

                    $set_i_to_zero = TRUE;
                } else
                {
                    $search_for_next_root = FALSE;
                    $sub_level = 1;
                }
            }
        }

        if ($set_i_to_zero)
        {
            $i = 0;
        } else
        {
            $i++;
        }
    }

    return $new;                                                
}

 $sorted = sort_array_by_levels ($menu);
 echo "<pre>";
 print_r ($sorted);
 echo "</pre>";