MyBB Hacks

• (Official?) Introduction to PHP - A Simple Tutorial - A very basic guide outlining what you need to do, and get familiar with PHP.  Note that the guide is extremely basic, and I wouldn't consider it enough for developing plugins/modifications
• Introduction to PHP - You can skip some of the steps, as you should already have a webserver set up.  The guide seems to be a decent overview of the basics of PHP.   If you read through this guide (PHP Basic section, PHP Advanced, you can leave till later), you should have sufficient knowledge to start writing some basic scripts.
  

<?php
function firstplugin_info()
{
	return array(
		'name'			=> 'My First Plugin',
		'description'	=> 'A plugin which does nothing.',
		'website'		=> 'http://',
		'author'		=> 'ME!!!',
		'authorsite'	=> 'http://',
		'version'		=> '1.0'
	);
}
?>

If you've read enough PHP, you should be able to recognize most of the above constructs.  We have declared a function, and the function returns a value - in this case, an array, containing the details of the plugin.  Note that the keys of the array are predefined - you generally shouldn't change them.
If you save the above code to /inc/plugins/firstplugin.php, it should show up in the AdminCP, with the details you specified.
Note, the filename and the prefix to the functions are important.  In the above, since the filename as firstplugin (we ignore the .php extension), the Info function must be named firstplugin_info.

Okay, the above plugin wasn't very exciting - let's look at a plugin which actually does more.

MyBB's Hello World
This plugin is something provided by MyBB to give a demonstration of the plugin system, but will serve our purposes of demonstration here.
Open up /inc/plugins/hello.php.  You should see the following:

<?php
/**
 * MyBB 1.2
 * Copyright © 2006 MyBB Group, All Rights Reserved
 *
 * Website: http://www.mybboard.net
 * License: http://www.mybboard.net/eula.html
 *
 * $Id: hello.php 2932 2007-03-10 05:48:55Z chris $
 */

// Disallow direct access to this file for security reasons
if(!defined("IN_MYBB"))
{
	die("Direct initialization of this file is not allowed.<br /><br />Please make sure IN_MYBB is defined.");
}

$plugins->add_hook("pre_output_page", "hello_world");
$plugins->add_hook("postbit", "hello_world_postbit");

function hello_info()
{
	return array(
		"name"			=> "Hello World!",
		"description"	=> "A sample plugin that prints hello world and changes the content of each post to 'Hello world!'",
		"website"		=> "http://www.mybboard.net",
		"author"		=> "MyBB Group",
		"authorsite"	=> "http://www.mybboard.net",
		"version"		=> "1.0",
	);
}

function hello_activate()
{
}

function hello_deactivate()
{
}

function hello_world($page)
{
	$page = str_replace("<div id=\"content\">", "<div id=\"content\"><p>Hello World!<br />This is a sample MyBB Plugin (which can be disabled!) that displays this message on all pages.</p>", $page);
	return $page;
}

function hello_world_postbit($post)
{
	$post['message'] = "<strong>Hello world!</strong><br /><br />{$post['message']}";
}
?>

You may, at first, realize that this is much more complex than the basic nutshell I posted above.
So let's break it down into pieces:

<?php
/**
 * MyBB 1.2
 * Copyright © 2006 MyBB Group, All Rights Reserved
 *
 * Website: http://www.mybboard.net
 * License: http://www.mybboard.net/eula.html
 *
 * $Id: hello.php 2932 2007-03-10 05:48:55Z chris $
 */

This is just the start of the PHP file, and the rest is just a comment, saying that this file is part of MyBB.  This can be ignored as this doesn't serve our purposes much.

// Disallow direct access to this file for security reasons
if(!defined("IN_MYBB"))
{
	die("Direct initialization of this file is not allowed.<br /><br />Please make sure IN_MYBB is defined.");
}

This piece of code is really optional, and the plugin will work fine without it.
The idea of the code is to stop a user directly accessing the file.
After reading PHP tutorials, most will explain to you about PHP files a user will access directly.  MyBB plugins, however, should only be include'd, and not accessed.
An example of directly accessing the file would be, a user going to http://example.com/forums/inc/plugins/hello.php
You do not have to worry too much on the details of how the code snippet works - you just need to know that the if statement will be true if a user access the file directly (and thus, the script will die).

$plugins->add_hook("pre_output_page", "hello_world");
$plugins->add_hook("postbit", "hello_world_postbit");

Okay, so now we see examples of adding hooks.  Again, I won't go into details of how it works - just assume that the function $plugins->add_hook exists and works well.
As you can see, we add hooks by calling the $plugins->add_hook() function.  The function has two required arguments - the name of the hook, and the name of our handler to the hook.
A list of available hooks can be found at the MyBB Wiki.
Hooks allow us to inject our own code into certain places in MyBB's code.  In the above example, the first line of code, hooks into the hook named pre_output_page.  This hook is run just before output data is sent to the user.  So what does this mean?  Basically, this tells MyBB, before the output is sent to the user, MyBB should execute the function named hello_world (which is defined later in the file).
Similarly, the second line tells MyBB to run the function named hello_world_postbit whenever it processes the hook postbit.  The postbit hook is executed every time just before a post is generated for showthread.

function hello_info()
{
	return array(
		"name"			=> "Hello World!",
		"description"	=> "A sample plugin that prints hello world and changes the content of each post to 'Hello world!'",
		"website"		=> "http://www.mybboard.net",
		"author"		=> "MyBB Group",
		"authorsite"	=> "http://www.mybboard.net",
		"version"		=> "1.0",
	);
}

This is just the required _info() function we talked about eariler.  You should be able to figure out what it does.

function hello_activate()
{
}

function hello_deactivate()
{
}

These demonstrate the optional _activate() and _deactivate() functions.  In this example, the functions do nothing (and, in this case, you could actually completely omit them).

function hello_world($page)
{
	$page = str_replace("<div id=\"content\">", "<div id=\"content\"><p>Hello World!<br />This is a sample MyBB Plugin (which can be disabled!) that displays this message on all pages.</p>", $page);
	return $page;
}

Remember the hooks we added?  This is the function definition for the pre_output_page hook we added eariler (in other words, this function is executed before the page output is sent to the user).
Note that the pre_output_page hook supplies an argument (most hooks don't supply an argument).  If you want to modify the argument, take it and return your modified version.
In the above case, the function calls str_replace(), which is a PHP function which replaces some text (see PHP manual for more details on this function).  After transforming the argument $page, the function simply returns it.

function hello_world_postbit($post)
{
	$post['message'] = "<strong>Hello world!</strong><br /><br />{$post['message']}";
}
?>

This is similar to the above function - it handles a plugin hook routine (postbit).
Instead of returning $post however, we just directly change it.  This is because the $post argument is actually passed by reference.  How passing by reference or value works is beyond this tutorial, but just remember that if something is passed by reference, you do not have to return a value.



Well, that's it for now.  Hopefully, you understood most things in this guide.  If you did, you should be able to write up some basic plugins.
If you don't know SQL, it's also probably a good time to learn it now.