display multilevel database driven menu in php - php

Question

I want to display a database driven Multilevel menu and below is what I have tried so far, but I am not getting the result as desired. Can any one help me to fix this. the output I am getting is only the main menu with parent id as 0, but not the sub menu items.
<?php
include('system/connection.php');
?>
<?php
//select all rows from the main_menu table
$q = "SELECT * FROM catelogue WHERE cat_visibility = '1'";
$r = mysqli_query($dbc, $q);
echo "<ul class='dropdown'>";
while ($rows = mysqli_fetch_assoc($r)) {
if ($rows['cat_parentid'] == 0) {
echo "<li><a href='#'>" . $rows['cat_name'] . "</a>";
echo "<ul>";
foreach ($rows as $item) {
if ($item['cat_parentid'] == $rows['cat_id']) {
echo "<li><a href='#'>" . $item['cat_name'] . "</a>";
echo "</li>";
}
}
echo "</ul>";
echo "</li>";
}
}
echo "</ul>";
?>
My Database structure is
-----------------------------------------
| cat_id | cat_name | cat_parentid |
-----------------------------------------
| 1 | Home | 0 |
| 2 | About | 0 |
| 3 | Contact | 0 |
| 4 | History | 2 |
| 5 | Services | 2 |
-----------------------------------------
Desired Output I want:
<ul class="dropdown">
<li><a href='#'>Home</a></li>
<li><a href='#'>About</a>
<ul>
<li><a href='#'>History</a></li>
<li><a href='#'>Services</a></li>
</ul>
</li>
<li><a href='#'>Contact</a></li>
</ul>

Answer 1

Here is a recursive solution.
The code is fully commented.
There are two useful checks in the processMenuEntry routine that can conveniently be done so that you can decide if you want different actions to happen.
Check whether the 'current' 'entry' is the 'root' node.
$isRoot = $currentEntry['cat_id'] == 0; // do 'First time' processing
Check whether the current 'entry' has a 'submenu'.
if (!empty($subMenu)) { ...
Q29910284-display-multilevel-database-driven-menu.php
The code:
Database connection:
$DB_HOST = "localhost";
$DB_USER = "test";
$DB_PASSWORD = "test";
$DB_TO_USE = "testmysql";
$dbc = new mysqli($DB_HOST, $DB_USER, $DB_PASSWORD, $DB_TO_USE);
Submenu Query:
/** -----------------------------------------------------------------
* Select all the menu entries for a given entry Id
*
* Note: it is safe to do 'parameter substitution' rather than using
* 'prepared queries' with placeholders as this 'entry Id' never
* comes from an external source.
*
* #param mysqli $dbc
* #param integer $currentEntryId
* #return array of menu entries
*/
function selectSubMenu($currentEntryId, $dbc)
{
$sql = "SELECT cat_id, cat_name, cat_parent_id
FROM catalogue
WHERE cat_parent_id = {$currentEntryId}
ORDER BY cat_id";
$resultSet = mysqli_query($dbc, $sql);
return $resultSet->fetch_all(MYSQLI_ASSOC);
}
Process Current Menu Entry:
/** --------------------------------------------------------------------------
* Process the current menu enty - it will return a complete menu as HTML
*
* These needs to know whether the current entry has a submenu and
* will therefore need to generate an 'unordered list' for the current entry.
*
* Alas, it also has to not display the 'list item text' for the 'root' entry
* but process the 'submenu'.
* This complicates the <li> current entry text generation slightly.
*
* #param array $currentEntry - one row
* #param array $subMenu - many rows - may be empty
* #param mysqli $dbc - database connection
* #return string - the HTML for the menu
*/
function processMenuEntry($currentEntry, array $subMenu, $dbc) {
$outMenu = '';
$isRoot = $currentEntry['cat_id'] == 0; // do 'First time' processing
// display the current entry text as a 'list item'
$outMenu .= !$isRoot ? "<li><a href='#'>" . $currentEntry['cat_name'] . "</a>" : '';
// does it have a submenu...
if (!empty($subMenu)) { // we need to add a complete submenu of <ul> ... </ul>
// Start of the submenu as an unordered list -- decide what is required
if ($isRoot) {
$outMenu .= '<ul class="dropdown">';
}
else {
$outMenu .= '<ul>';
}
// Display each entry of the submenu as a 'list item'
foreach ($subMenu as $submenuEntry) {
$outMenu .= processMenuEntry($submenuEntry,
selectSubMenu($submenuEntry['cat_id'], $dbc),
$dbc);
}
// close the current submenu - terminate the unordered list
$outMenu .= '</ul>';
}
// terminate the current list item
$outMenu .= !$isRoot ? '</li>' : '';
return $outMenu;
};
Process all the menu entries:
/* -------------------------------------------------------------------
* Process all the menu entries
*
* We need a complete menu 'tree' that includes a 'root' which is not provided
* in the database. I think it should be. Whatever, i need one.
*
* Initializing a 'tree walk' i always find 'interesting' ;-/
*/
$root = array('cat_id' => 0, 'cat_name' => '', 'cat_parent_id' => 0);
// build the output menu
$outMenu = processMenuEntry($root,
selectSubMenu($root['cat_id'], $dbc),
$dbc);
// wrap it in a <div>
$htmlMenu = '<div style="border: 1px solid red">'
. $outMenu
.'</div>';
?>
Output the generated HTML:
<!DOCTYPE html>
<html>
<head>
<title>Test Recursive Menu Builder</title>
</head>
<body>
<?= $htmlMenu ?>
</body>
</html>
The generated HTML
<!DOCTYPE html>
<html>
<head>
<title>Test Recursive Menu Builder
</title>
</head>
<body>
<div style="border: 1px solid red">
<ul class="dropdown">
<li>
<a href='#'>Home</a>
</li>
<li>
<a href='#'>About</a>
<ul>
<li>
<a href='#'>History</a>
</li>
<li>
<a href='#'>Services</a>
</li>
</ul>
</li>
<li>
<a href='#'>Contact</a>
</li>
</ul>
</div>
</body>
</html>

Answer 2

What you call $rows is actually one row. Then, in the foreach ($rows as $item) loop, it iterates through the columns of this row. So, there is no $item['cat_parentid']. Try to see the output of the $rows and $item with var_dump().
A draft idea of one possible solution that comes to my mind is to first iterate through the result rows and save the sub items in a parent item (note: some array initializations would have to be added here):
while ($row = mysqli_fetch_assoc($r)) {
$menuItems[$row['cat_id']] = $row;
$parentId = $row['cat_parentid'];
$menuItems[$parentId]['sub_items'][] = $row['cat_id'];
}
And then iterate through the $menuItems array generating output, recursion would be great for this.
Also, ordering the sql results would be beneficial, to be sure that top menu items come first:
"SELECT * FROM catelogue WHERE cat_visibility = '1' ORDER BY cat_parentid ASC";