UltraMega Blog
9Feb/104

PHP: Recursive Functions

A recursive function is a function that calls itself. This is useful for certain applications. This short tutorial will show an example of a recursive function in action.

Let's say we have the following array of categories. Normally this might be stored in a database, but we'll use an array here for simplicity.

/* Example category hierarchy:
    Tutorials
    - PHP
    -- OOP
    -- Tips
    - JavaScript
    -- Basics
    -- Frameworks
    --- jQuery
    --- MooTools
    News
    - PHP
    - Wordpress
*/
$cats = array();
$cats[1] = array('parent' => 0, 'title' => 'Tutorials');
  $cats[2] = array('parent' => 1, 'title' => 'PHP');
    $cats[3] = array('parent' => 2, 'title' => 'OOP');
    $cats[4] = array('parent' => 2, 'title' => 'Tips');
  $cats[5] = array('parent' => 1, 'title' => 'JavaScript');
    $cats[6] = array('parent' => 5, 'title' => 'Basics');
    $cats[7] = array('parent' => 5, 'title' => 'Frameworks');
      $cats[8] = array('parent' => 7, 'title' => 'jQuery');
      $cats[9] = array('parent' => 7, 'title' => 'MooTools');
$cats[10] = array('parent' => 0, 'title' => 'News');
  $cats[11] = array('parent' => 10, 'title' => 'PHP');
  $cats[12] = array('parent' => 10, 'title' => 'Wordpress');

In this case, a good application of a recursive function would be to display a breadcrumbs display of a particular category. In the example, we use the key 'parent' to identify the category that a subcategory belongs to, or 0 for the main categories.

2Feb/106

Using a PHP Class to Store Configuration

In a comment on my post listing 5 Tips for Writing Cleaner PHP Code, some good arguments were made against using constants to store configuration variables. The main arguments is that it pollutes the global namespace, which can lead to collisions when implementing other code, and the way it handles typos. This article demonstrates some of the ways constants can fail, and shows an alternative.

So here is how to store these constants in a class to avoid these problems. This puts the constants in their own namespace and prevent mistakes later on.

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<?php
 
// Declaring your config class constants
class Config {
    const DB_HOST     = 'localhost',
          DB_USER     = 'username',
          DB_PASS     = 'password',
          ANOTHER_VAR = true;
}
 
echo Config::DB_HOST; // outputs localhost
 
echo Config::USER; // PHP Fatal error
 
if(Config::ANOTHER_VAR) {
    // do something
}
 
?>

That's all there is to it. Now all your constants are consolidated under one namespace and any typos will result in a fatal error. You can name the class whatever you want to be unique and avoid any collisions.

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