How to build a tree view with PHP / SQL? - php

Question

What's the best way to:
Get the data from the db using a single query
Loop through the results building e.g. a nested unordered list
My table has id, name and parent_id columns.
Here's an update to my last answer, with a counter that gives each ul a nesting 'level' class, and some comments.
Could anyone suggest how to adapt this to use table rows, without nesting, but with some kind of class numbering hierarchy for css/js hooks?
<?
//
// Get the data
//
include_once("inc/config.php");
$query = "SELECT c.*
FROM categories AS c
ORDER BY c.id
LIMIT 1000";
$result = pg_query($db, $query);
//
// Load all the results into the row array
//
while ($row = pg_fetch_array($result, NULL, PGSQL_ASSOC))
{
//
// Wrap the row array in a parent array, using the id as they key
// Load the row values into the new parent array
//
$categories[$row['id']] = array(
'id' => $row['id'],
'description' => $row['description'],
'parent_id' => $row['parent_id']
);
}
// print '<pre>';
// print_r($category_array);
// ----------------------------------------------------------------
//
// Create a function to generate a nested view of an array (looping through each array item)
// From: http://68kb.googlecode.com/svn-history/r172/trunk/upload/includes/application/controllers/admin/utility.php
//
function generate_tree_list($array, $parent = 0, $level = 0)
{
//
// Reset the flag each time the function is called
//
$has_children = false;
//
// Loop through each item of the list array
//
foreach($array as $key => $value)
{
//
// For the first run, get the first item with a parent_id of 0 (= root category)
// (or whatever id is passed to the function)
//
// For every subsequent run, look for items with a parent_id matching the current item's key (id)
// (eg. get all items with a parent_id of 2)
//
// This will return false (stop) when it find no more matching items/children
//
// If this array item's parent_id value is the same as that passed to the function
// eg. [parent_id] => 0 == $parent = 0 (true)
// eg. [parent_id] => 20 == $parent = 0 (false)
//
if ($value['parent_id'] == $parent)
{
//
// Only print the wrapper ('<ul>') if this is the first child (otherwise just print the item)
// Will be false each time the function is called again
//
if ($has_children === false)
{
//
// Switch the flag, start the list wrapper, increase the level count
//
$has_children = true;
echo '<ul class="level-' . $level . '">';
$level++;
}
//
// Print the list item
//
echo '<li>' . $value['description'] . '';
//
// Repeat function, using the current item's key (id) as the parent_id argument
// Gives us a nested list of subcategories
//
generate_tree_list($array, $key, $level);
//
// Close the item
//
echo '</li>';
}
}
//
// If we opened the wrapper above, close it.
//
if ($has_children === true) echo '</ul>';
}
// ----------------------------------------------------------------
//
// generate list
//
generate_tree_list($categories);
?>

Answer 1

function generate_list($array,$parent,$level)
{
foreach ($array as $value)
{
$has_children=false;
if ($value['parent_id']==$parent)
{
if ($has_children==false)
{
$has_children=true;
echo '<ul>';
}
echo '<li>'.$value['member_name'].' -- '.$value['id'].' -- '.$value['parent_id'];
generate_list($array,$value['id'],$level);
echo '</li>';
}
if ($has_children==true) echo '</ul>';
echo $value['parent_id'];
}
}

Answer 2

MySQL have created a good article on this subject: Managing Hierarchical Data in MySQL

Answer 3

You can create a breadcrumb view style by using arrays, without using a recursive function.
Here is my working code:
First, make a SQL query like this:
$category = CHtml::listData(TblCategory::model()->findAllCategory(array(
'distinct'=>true,
'join'=>'LEFT JOIN tbl_category b on b.id = t.cat_parent',
'join'=>'LEFT JOIN tbl_category c on c.cat_parent = 0',
'order' => 'cat_name')),'id','cat_name');
I am using yii related code so you can use normal join queries, then form an array in a foreach() function
public function findAllCategory($condition='',$params=array())
{
Yii::trace(get_class($this).'.findAll()','system.db.ar.CActiveRecord');
$criteria=$this->getCommandBuilder()->createCriteria($condition,$params);
$category = array();
$cat_before;
$parent_id = array();
$cat_before = $this->query($criteria,true);
//echo "<br><br><br><br><br><br><br>";
foreach($cat_before as $key => $val)
{
$category[$key] = $val;
$parent_id[$key]['cat_parent'] =$val['cat_parent'];
$parent_id[$key]['cat_name'] =$val['cat_name'];
foreach($parent_id as $key_1=> $val_1)
{
if($parent_id[$key]['cat_parent'] == $category[$key_1]['id'])
{
$category[$key]['cat_name']= $category[$key_1]['cat_name'] .' > '. $parent_id[$key]['cat_name'];
}
}
}
return $cat_before;
}
Then you can get result using Main cat >> subcat 1 >> subcat_1 inner >> ...