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Rounding Up The Family - PHP

So you know the theory behind OOP, but don't really understandits applications? Well, it's time to take objects out of the classroom andinto the real world - this article demonstrates how OOP can save you timeand effort by building a PHP-based Menu object to describe therelationships in a hierarchical menu tree. And since the proof of thepudding is in the eating, it then combines the newly-minted Menu objectwith some of the most popular JavaScript menu systems available online toshow you how cool objects really are.

  1. Building an Extensible Menu Class
  2. Back To Class
  3. What's On The Menu?
  4. Children And Their Parents
  5. I Say Method, You Say Madness...
  6. Rounding Up The Family
  7. Saving My Bookmarks
  8. Reaching Higher
  9. Collapsing Inwards
  10. Extending Yourself
By: Team Melonfire, (c) Melonfire
Rating: starstarstarstarstar / 6
August 10, 2001

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Next, one of the most useful methods in this collection - the get_children() method. This method accepts a node id and returns an array containing the next level of the menu tree.

<? class Menu { // other methods // function: get next level of menu tree // returns: array function get_children($id) { $query = "SELECT id, label, link FROM $this->table WHERE parent = '$id'"; $result = $this->query($query); $count = 0; while ($row = mysql_fetch_array($result)) { $children[$count]["id"] = $row["id"]; $children[$count]["label"] = $row["label"]; $children[$count]["link"] = $row["link"]; $count++; } return $children; } } ?>
This method accepts a node id and queries the database for a list of items which reference that node in the "parent" column. These records are packaged as an array of arrays and returned to the calling function. Here's an example of how it could be used:

<? $obj = new Menu(); // get children $arr = $obj->get_children(1); echo "<ul>"; // iterate through array for ($x=0; $x<sizeof($arr); $x++) { echo "<li>" . $arr[$x]["label"]; } echo "</ul>"; ?>
And this correctly displays the children of node id 1 (USA) to be

California Massachusetts
A useful corollary of this is the get_type() method, which can be 
used to identify whether a particular node on the tree has children or not - in other words, whether it is a leaf or a branch. 

<? class Menu { // other methods // function: test whether this id is a branch or leaf // returns: boolean function get_type($id) { if($this->get_children($id) ) { return 1; } else { return 0; } } } ?>
The get_ancestors() method does the reverse of the get_children() method - it returns a list of nodes between the tree root and the supplied node identifier, starting from the top of the menu tree and proceeding downwards.

<? class Menu { // other methods // function: return a list of this node's parents // by travelling upwards all the way to the root of the tree // returns: array function get_ancestors($id, $count = 0) { // get parent of this node $parent = $this->get_parent($id); // if not at the root, add to $ancestors[] array if($parent) { $this->ancestors[$count]["id"] = $parent; $this->ancestors[$count]["label"] = $this->get_label($parent); $this->ancestors[$count]["link"] = $this->get_link($parent); // recurse to get the parent of this parent $this->get_ancestors($this->ancestors[$count]["id"], $count+1); // all done? at this stage the array contains a list in bottom-up order // reverse the array and return return array_reverse($this->ancestors); } } } ?>
Returning to the example above, an attempt to find out the ancestors of node id 5 (Boston)

<? $obj = new Menu(); // get children $arr = $obj->get_ancestors(5); echo "<ul>"; // iterate through array for ($x=0; $x<sizeof($arr); $x++) { echo "<li>" . $arr[$x]["label"]; } echo "</ul>"; ?>
would return

USA Massachusetts
Finally, the print_menu_tree() method comes in handy while debugging, 
if you need to visually see the complete menu tree with its internal dependencies. 

<? class Menu { // other methods // function: display complete menu tree (useful when debugging) // returns: HTML list function print_menu_tree($id = 0) { $result = $this->get_children($id); echo "<ul>"; for ($x=0; $x<sizeof($result); $x++) { echo "<li>" . $result[$x]["label"] . "[" . $result[$x]["id"] . "]"; $this->print_menu_tree($result[$x]["id"]); } echo "</ul>"; } } ?>

>>> More PHP Articles          >>> More By Team Melonfire, (c) Melonfire

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