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Deciphering Magic Methods in PHP

Deciphering Magic Methods in PHP | Nettuts+

PHP provides a number of ‘magic’ methods that allow you to do some pretty neat tricks in object oriented programming. These methods, identified by a two underscore prefix (__), function as interceptors that are automatically called when certain conditions are met. Magic methods provide some extremely useful functionality, and this tutorial will demonstrate each method’s use.

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Round Robin Tournament Scheduler

Here's a snippet I wrote for a project that I thought might come in handy for someone else. It generates a schedule for a round robin tournament. I found some other snippets to do this, but I found them overly complicated or lacking in other ways.

Here's an example of what this code does:

< ?php
$players = range(1, 8);
echo 'Original List: ' . PHP_EOL;
echo PHP_EOL;
echo 'Round Robin Schedule: ' . PHP_EOL;


Original List: 
    [0] => 1
    [1] => 2
    [2] => 3
    [3] => 4
    [4] => 5
    [5] => 6
    [6] => 7
    [7] => 8
Round Robin Schedule: 
    [0] => Array
            [0] => Array
                    [0] => 1
                    [1] => 8
            [1] => Array
                    [0] => 2
                    [1] => 7
            [2] => Array
                    [0] => 3
                    [1] => 6
            [3] => Array
                    [0] => 4
                    [1] => 5

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:
    - PHP
    -- OOP
    -- Tips
    - JavaScript
    -- Basics
    -- Frameworks
    --- jQuery
    --- MooTools
    - 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.


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.

// 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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Using SSH in PHP

This tutorial will show you how to use the SSH2 functions in PHP to execute commands over SSH. This requires the SSH2 PECL extension to be installed on your server (installation instructions). Keep in mind that as of this time, the extension is in a beta state, so stability is not guaranteed.

Sending commands is fairly straightforward. You just connect, authenticate, then execute commands. Authentication can be done using a password or public key. Executing commands is a little tricky since it returns a stream that you have to handle.

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PHP in the Shell

PHP may be most commonly used within a web server to produce web pages, but it is a powerful scripting engine by itself. PHP is an amazingly useful multipurpose tool when used from the command line. This post will show you how to use the PHP Command Line Interface (CLI). Some of the information here is Linux specific, but there are equivalents for Windows.

Accessing the PHP CLI

Obviously the first thing you need to know is how to run PHP from the command line. There are a number of ways to do this, and one way that I prefer.

The method I find easiest is to write your script as a shell script. This basically means taking a regular PHP script and adding a line to the beginning declaring the php binary to interpret the script. Here's an example:

< ?php
echo 'Hello World';

Assuming the file name 'test.php' you would make it executable with chmod +x test.php and run it simply with ./test.php. Note that the file does not need to end with .php to function.

Other options for accessing the PHP CLI are to pass scripts or code to php as parameters, pass code to php through standard input, or enter code manually in interactive mode.

File as parameter:

$ php test.php

Code as parameter:

$ php -r "echo 'Hello World';"

Code through standard input (generate_php_code outputs code):

$ generate_php_code | php

Interactive mode:

$ php -a
Interactive shell
php > echo 'Hello World';
Hello World
php >