Creating a PHP-Based Content Management System

part one

i will ad the part tow in few days

If you’re going to run an intranet site, then you’ll probably want a content management system (CMS) — a tool used to organize documents and keep track of what’s where. I’ve covered a plethora of such systems in previous articles, but for many businesses there can be only one solution: to design and implement their own custom system.

Why? It’s not like the off-the-shelf systems lack features or stability. On the contrary, many have been crafted by hundreds of man-hours of work, and are successfully implemented by thousands of Web sites and intranets. But when it comes down to it, it’s hard to have much clue as to how they work. If you want to customize the way these systems operate, you’ll often have to wade through vast amounts of (often badly documented) code to find what needs changing.

Writing your own CMS, on the other hand, can lead to a solution that is better suited to your requirements, better addresses the needs of your users, and is better understood by your development team. If you have the time and expertise to write your own in-house system, it may well prove the better option. And this is what I shall be embarking upon in this series.

The system we create will be written using the PHP programming language, which excels in the development of Web-based systems. I’ll be using MySQL as the database server, but the system will be written to allow the use of alternative databases, such as PostgreSQL or SQL Server.

So what will this system actually do? First and foremost, it will allow the bulk of the intranet or Internet site’s content to be easily stored and managed in a database. We’ll also include a number of other features required for running a successful site, such as authenticating users and managing files.

Some basic PHP knowledge will be needed for coding your own CMS, although most of what you’ll need to know will be demonstrated here. I’ll assume you have access to a server running PHP and a database system. Once the series is complete, I’ll make available a polished version of the CMS for anyone to use.

I don’t promise the vast array of abilities incorporated into systems such as Postnuke, Smarty, or some commercial content management systems. But just having lots of features isn’t always what’s needed, and this series will help you to develop a system specifically targeted to your needs. With that, let’s get going…

Planning the CMS

To begin with, we’ll plan how our PHP-based content management system will work. In subsequent articles, I’ll demonstrate how each of the major components are implemented, leading to a complete system.

The first step is a basic specification of what our CMS must do. Obviously, this will depend on your needs:

• Content Management: Probably the most vital function of the system, it must store content such as documents and news in a database, and display to the user whatever he or she requests. An easy-to-use interface is required to allow editors to add, remove, or modify content.
• User authentication: There may be certain areas of the intranet or Internet site to which we wish to limit access. At the very least this will be the “admin” area, where the editor of the site will be able to add, edit or modify content. You may also wish to have areas only available to certain departments or staff.
• Page uniformity/templates: The system should have a uniform look and feel, and this design element needs to be separated from the logic element, e.g., the programming required to display an article should be separated from how that article looks (stylistically) on the screen.

Object-Oriented Programming

PHP helps the design process by supporting object-oriented programming (OOP). When putting together our system, there are certain chunks of programming that are needed again and again, such as database access, user authentication, etc. To keep this code neat and tidy, we bundle it together in PHP files called “classes.” We can then create instances (or “objects”) of these classes whenever they are needed. Thus, the class can be thought of as a blueprint for one or more instances.

For example, we could create a class with code for connecting to a database, and then create an instance of that class whenever we need to query the database. If this isn’t immediately clear then don’t worry, it will become more obvious when we start coding. This method of programming allows a complex system to be broken down into smaller and simpler blocks, which makes life easier when it comes to management, modification, and error finding.

Let’s now consider how the system will fit together. This will doubtless be tweaked as you consider the requirements for your own system, but below is a basic outline:

We have four main PHP modules (or “classes”) that will be widely used in the system. These are tasked with accessing the database, allowing the user to upload files to the site, reading and writing templates, and logging users in and out. These classes all “extend” one parent class called “systemObject.”

Think of these four as being independent of one another, yet all inheriting whatever data we put in systemObject. This technique of hierarchy allows us to make changes effecting all four system classes, just by adding or modifying the code in the systemObject parent class. Again, this concept will become clearer when we start coding. In the middle of the diagram are the basic areas of the administration system, and each will need one or more PHP pages to perform the required tasks.

This article requires a basic knowledge of PHP programming, although a number of concepts are explained for those less experienced.

Our CMS will be stored in a number of folders, structured as follows:

You may wish to create these four folders now. We’re going to start by creating the PHP class which all others will “extend.” This will be the root of the administration system, and anything we put in it (such as variables and functions) will trickle down to the other classes.

This root class will be called ‘SystemComponent’. The code follows, and a full explanation is below:

<?php
class SystemComponent {

var $settings;

function getSettings() {

// System variables
$settings['siteDir'] = ‘/path/to/your/intranet/’;

// Database variables
$settings['dbhost'] = ‘hostname’;
$settings['dbusername'] = ‘dbuser’;
$settings['dbpassword'] = ‘dbpass’;
$settings['dbname'] = ‘mydb’;

return $settings;

}

}
?> Reminder: A class is a block of code. Whenever we need to run that code, we create an ‘object’ or ‘instance’ of the class. We can create as many instances of a class as we like. If you don’t understand objects and classes by the end of this article, I recommend getting a book or finding a Web site on Object Oriented Programming.

The above code starts off by telling PHP that our class will be called ‘SystemComponent’. Between the braces (squiggly brackets) we declare the variable $settings, and a function called ‘getSettings’. The purpose of this is to store a number of values in $settings, containing the path on the server to the intranet (’siteDir’), and the details of the database. Change these appropriately for the database system you’ll be using (this tutorial uses MySQL, more details coming up). Finally, the ‘return’ command sends $settings to whichever class or function has requested it. We’ll be storing more data in $settings as the series progresses.

Save this code to a file called SystemComponent.php in the ‘includes’ folder you created. Now let’s do something with this class.

All of the information to be displayed in our Content Management System will be stored in a database. It is sensible, therefore, to create a reusable PHP class that we can call upon whenever we need to access our data. The code listed here is for connecting to a MySQL database. If you’ll be using a different system, such as PostgreSQL, MS SQL or SQLite, then change the code appropriately. It’s obviously quite a bit longer than our previous class, but it performs a number of very important tasks. The code follows:

<?php
////////////////////////////////////////////////////////////////////////////////////////
// Class: DbConnector
// Purpose: Connect to a database, MySQL version
///////////////////////////////////////////////////////////////////////////////////////
require_once ‘SystemComponent.php’;

class DbConnector extends SystemComponent {

var $theQuery;
var $link;

//*** Function: DbConnector, Purpose: Connect to the database ***
function DbConnector(){

// Load settings from parent class
$settings = SystemComponent::getSettings();

// Get the main settings from the array we just loaded
$host = $settings['dbhost'];
$db = $settings['dbname'];
$user = $settings['dbusername'];
$pass = $settings['dbpassword'];

// Connect to the database
$this->link = mysql_connect($host, $user, $pass);
mysql_select_db($db);
register_shutdown_function(array(&$this, ‘close’));

}

//*** Function: query, Purpose: Execute a database query ***
function query($query) {

$this->theQuery = $query;
return mysql_query($query, $this->link);

}

//*** Function: fetchArray, Purpose: Get array of query results ***
function fetchArray($result) {

return mysql_fetch_array($result);

}

//*** Function: close, Purpose: Close the connection ***
function close() {

mysql_close($this->link);

}

}
?>

Some explanation is required. After we’ve named the class ‘DbConnector’, we state ‘extends SystemComponent’. This tells PHP to grab all of the data and functions from SystemComponent, and provide us with access to them (we’ll need this in order to get the $settings variable we created earlier).

The first function, ‘DbConnector’, has the same name as the class that contains it, meaning it’s run automatically when DbConnector loads. It firstly calls the ‘getSettings’ function we wrote earlier, and extracts from it the various database settings. It then uses these settings to connect to the database. (Note that we have no code to deal with errors, this will be covered in detail next time.)

The other functions are explained below:

Function

Purpose

Save the above code (also attached at the bottom of this article) to the ‘includes’ folder, with the name DbConnector.php. This class will be widely used in the Intranet system, so let me give you an example of how we’d create an instance of DbConnector, extract some data, and display it to the user. Let’s imagine that our database stores the details of one customer, and we want to get hold of his / her name and display it. Here’s the code:

<?php

// Get the PHP file containing the DbConnector class
require_once(‘DbConnector.php’);

// Create an instance of DbConnector
$connector = new DbConnector();

// Use the query function of DbConnector to run a database query
// (The arrow -> is used to access a function of an object)
$result = $connector->query(‘SELECT firstname FROM customers’);

// Get the result
$row = $connector->fetchArray($result);

// Show it to the user
echo $row['firstname'];

?>

If you’d like to try out the DbConnector class now, you’ll need to save the above code in the includes folder in a php file, and set up a ‘customers’ table in your database. I’ll be covering the set up of our Intranet’s database next time.

The importance and power of using a database is clear – we can store information in a formal way, and rapidly access, manipulate and change it. The information we extract or store is specified using the ‘query’ function of the DbConnector class, and we create instances of DbConnector using the ‘new’ command, as shown above. This also demonstrates the usefulness of classes – if the settings are changed in SystemComponent, then all of the classes that extend it will automatically be changed.

Creating the Database

The first table we’re going to add to our database will store articles, for display on the Intranet. The ability to share information is the most important function of an Intranet, and the job of the Content Management System is to make doing this as easy as possible. Consider your own data requirements, a few important ones spring to mind for most articles tables:

Field	Purpose	Type
ID	A unique number given to each article, and the primary key of the table.	Integer
Title	The title of the article	Varchar(300)
Tagline	A very short summary of the article	Varchar(600)
Section	The category to which the article belongs	Integer
TheArticle	The article itself	Text

Before we can create the system itself, we need to create the database to store our information. The code below will set this up if you’re using the MySQL database system – uses of other systems should modify the commands appropriately. Copy and paste the following into the MySQL admin tool, or use one of the many free ‘client’ programs available:

CREATE TABLE `databasename`.`cmsarticles` (
`ID` int(6) unsigned NOT NULL auto_increment COMMENT ‘The unique ID of the article’,
`title` varchar(200) NULL COMMENT ‘The article title’,
`tagline` varchar(255) NULL COMMENT ‘Short summary of the article’,
`section` int(4) NULL DEFAULT 0 COMMENT ‘The section of the article’,
`thearticle` text NULL COMMENT ‘The article itself’,
PRIMARY KEY (`ID`)
);

If all has gone to plan, you should now have a working table in the database. We’re now going to create a page to allow you or your staff to enter articles into the system.

Creating the editor

Firstly, design a form using the HTML editor of your choice. Create text fields for each database field (excluding ID). An example is below:

Title:Tagline:Section:Article: