Introduction
MVC architectural pattern is almost in everywhere today, whether you are working on Java, C#, PHP, iOS projects. This might not be 100% exact, but PHP community has the most amount of MVC frameworks. Today you might be using Zend, tomorrow on another project you might have to change to Yii or Laravel or CakePHP. If you are new to MVC frameworks and you just download one from the official website, you might feel overwhelmed when you look at the framework’s source code, yes, it is complex, as these popular frameworks are not written in a month - they are published, refined, tested again and again, and the functionalities are added constantly. So from my experience, knowing the core design methodologies of MVC framework is critical, otherwise you might feel that you will have to learn another framework and another framework again and again when you get new projects using new frameworks.
The best way to understand MVC is to write you own MVC framework from scratch! In this series of articles I am going to show you how to code one, so that you might get to understand why certains things happen that way in a framework.
MVC architectural pattern
M: Model
V: View
C: Controller
The core concept of MVC is to separate business logic from displaying(the View part). First let me explain the whole workflow of an HTTP request & HTTP response. For example, we have a commerce website and we want to add a certain product. A very simple URL would be look like this:
http://bestshop.com/index.php?p=admin&c=goods&a=add
http://bestshop.com is the domain name or base URL;
p=admin means the Platform is admin panel, or the Backend site of the system. We also have a Frontend site, which is public to the world(in this case, it would be p=public)
c=goods&a=add means this URL requests the ‘goods’ Controller’s add action method.
Front Controller Design Pattern
What is index.php in the above example? This file is called ‘Front Controller’ in PHP’s MVC frameworks. The name is usually index.php, but you can name it something else(few people do that thought…) One of the function of this index.php file is, it works as the single entry point for any HTTP requests, that is, no matter what resource you request in the URL, it will all go into this index.php file first. But why? How does the magic happen? Front Controller design pattern is implemented in PHP using Apache HTTP server’s distribution configuration file called .htaccess. In this file, we can tell the Apache HTTP server to redirect all requests to index.php using its rewrite module. You can code similar to this:
<IfModule mod_rewrite.c>
Options +FollowSymLinks
RewriteEngine on
# Send request via index.php
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.*)$ index.php/$1 [L]
</IfModule>
This configuration file is very powerful and when you change it, you don’t need to restart Apache. If you change Apache’s other configuration files, you need to restart it, the reason is that for other Apache configuration files, Apache only will read them when it’s started, that’s why any change requires a restart(Apache is mainly written in C by the way). But for .htaccess distribution configuration file, no restart is needed for any change.
Simply put, index.php will also do the proper initialization for the framework and it will route the request to the proper Controller(goodsController in above example) and an action method(member function) within that Controller class.
Our MVC Framework’s Structure
So let’s create our frameworks structure.
application directory is the web app’s directory;
framework directory is for the framework itself;
public directory is to store all the public static resources like html, css and js files.
index.php is the ‘entry-point’ file, the front controller.
Now within application folder, we create these subfolders:
config - stores the app’s configuration files
controllers - this is for all app’s Controller classes
model - this is for all app’s Model classes
view - this is for all app’s View classes
Now within the application/controllers folder, we will create two folders for the frontend and backend platforms:
And in the view folder, the same for frontend and backend:
As you can see, within the application folder, we created frontend and backend subfolder in controllers and views folder, as our application has a frontend site and a backend site. But why we did not do the same in the models folder?
Well, the reason here is, normally for a web app:
Frontend and Backend can be two different ‘websites’, but the are CRUD the same database, that’s why an internal user updated a product’s price, the price is immediately show on the frontend public page - backend and frontend share the same database/tables.
So that’s why both backend and frontend can share a set of Model classes, and that’s why we didn’t create separate folders in the models folder.
Now let’s move on to the framework directory, some frameworks name this folder using the framework’s name, say ‘symfony’. In this folder, we quickly create these subfolders first:
core - it will store the framework’s core classes
database - database related classes, such as database driver classes
helpers - help/assistant functions
libraries - for class libraries
Now move on to the public folder, we create these subfolders:
css - for css files
images - for images files
js - for javascript files
uploads - for uploaded files, such as uploaded images
Ok, so far this is our mini MVC framework’s structure.
Framework’s core class
Now under framework/core folder, we’ll create the framework’s first class - Framework.class.php in framework/core folder
// framework/core/Framework.class.php
class Framework {
public static function run() {
echo "run()";
}
we created a static function called run(). Now test it in index.php:
<?php
require "framework/core/Framework.class.php";
Framework::run();
You can see the result in browser(how to config your virtual host is skipped here). Normally this static function is called run() or bootstrap(). Within this function, we can do 3 main things here, as shown in the code below:
Copy Codeclass Framework {
public static function run() {
// echo "run()";
self::init();
self::autoload();
self::dispatch();
}
private static function init() {
}
private static function autoload() {
}
private static function dispatch() {
}
}
Initialization
Here is the code for the init() method:
Copy Code// Initialization
private static function init() {
// Define path constants
define("DS", DIRECTORY_SEPARATOR);
define("ROOT", getcwd() . DS);
define("APP_PATH", ROOT . 'application' . DS);
define("FRAMEWORK_PATH", ROOT . "framework" . DS);
define("PUBLIC_PATH", ROOT . "public" . DS);
define("CONFIG_PATH", APP_PATH . "config" . DS);
define("CONTROLLER_PATH", APP_PATH . "controllers" . DS);
define("MODEL_PATH", APP_PATH . "models" . DS);
define("VIEW_PATH", APP_PATH . "views" . DS);
define("CORE_PATH", FRAMEWORK_PATH . "core" . DS);
define('DB_PATH', FRAMEWORK_PATH . "database" . DS);
define("LIB_PATH", FRAMEWORK_PATH . "libraries" . DS);
define("HELPER_PATH", FRAMEWORK_PATH . "helpers" . DS);
define("UPLOAD_PATH", PUBLIC_PATH . "uploads" . DS);
// Define platform, controller, action, for example:
// index.php?p=admin&c=Goods&a=add
define("PLATFORM", isset($_REQUEST['p']) ? $_REQUEST['p'] : 'home');
define("CONTROLLER", isset($_REQUEST['c']) ? $_REQUEST['c'] : 'Index');
define("ACTION", isset($_REQUEST['a']) ? $_REQUEST['a'] : 'index');
define("CURR_CONTROLLER_PATH", CONTROLLER_PATH . PLATFORM . DS);
define("CURR_VIEW_PATH", VIEW_PATH . PLATFORM . DS);
// Load core classes
require CORE_PATH . "Controller.class.php";
require CORE_PATH . "Loader.class.php";
require DB_PATH . "Mysql.class.php";
require CORE_PATH . "Model.class.php";
// Load configuration file
$GLOBALS['config'] = include CONFIG_PATH . "config.php";
// Start session
session_start();
}
From the comments you can see the purpose of each steps.
Autoloading
We don’t want to manually code include or require for a class file what we need in every script in the project, that’s why PHP MVC frameworks have this autoloading feature. For example, in Symfony, if you put your own class file under ‘lib’ folder, then it will be auto loaded. Magic? No, there is no magic. Let’s implement our autoloading feature in our mini framework.
Here we need to use a PHP built-in function called spl_autoload_register
Copy Code// Autoloading
private static function autoload(){
spl_autoload_register(array(__CLASS__,'load'));
}
// Define a custom load method
private static function load($classname){
// Here simply autoload app’s controller and model classes
if (substr($classname, -10) == "Controller"){
// Controller
require_once CURR_CONTROLLER_PATH . "$classname.class.php";
} elseif (substr($classname, -5) == "Model"){
// Model
require_once MODEL_PATH . "$classname.class.php";
}
}
Every framework has a name conversion, ours is no exception. For a controller class, it should be xxxController.class.php, for a model class, it should be xxxModel.class.php. Why for a new framework you come across, you must follow its naming convention? Autoloading is one of the reasons.
Routing/Dispatching
// Routing and dispatching
private static function dispatch(){
// Instantiate the controller class and call its action method
$controller_name = CONTROLLER . "Controller";
$action_name = ACTION . "Action";
$controller = new $controller_name;
$controller->$action_name();
}
In this step, index.php will dispatch the request to the proper Controller::Action() method. It’s very simple here just for an example.
Base Controller class
There is always a base controller class(or several) in the framework’s core classes. For example, In Symfony it’s called sfActions; in iOS it’s called UIViewController. Here we will just name it Controller, the file name is Controller.class.php
Copy Code<?php
// Base Controller
class Controller{
// Base Controller has a property called $loader, it is an instance of Loader class(introduced later)
protected $loader;
public function __construct(){
$this->loader = new Loader();
}
public function redirect($url,$message,$wait = 0){
if ($wait == 0){
header("Location:$url");
} else {
include CURR_VIEW_PATH . "message.html";
}
exit;
}
}
Base Controller has a property called $loader, it is an instance of Loader class(introduced later). Please note the phrase ‘ it is an instance of Loader class’ -- preciously speaking, $this->loader is a reference variable which reference/points to an instance of Load class. We don’t talk more about this here, but this is actually a very important concept. I have met some PHP developers who believe after this statement:
$this->loader = new Loader();
$this->loader is an object. No, it’s a reference. This term starts from Java, before Java, it’s called pointer in C++ or Objective C. Reference is an encapsulated pointer type. For example, in iOS(Objective-C) we create an object using:
UIButton *btn = [UIButton alloc] init];
Loader class
In framework.class.php, we have already implemented application’s controller and model class’ autoloading. But how to load classes in the framework directory? Here we can create a new class called Loader, it will be used to load the framework’s classes and functions. When we need to load a framework’s class, just call this Loader class’s method.
class Loader{
// Load library classes
public function library($lib){
include LIB_PATH . "$lib.class.php";
}
// loader helper functions. Naming conversion is xxx_helper.php;
public function helper($helper){
include HELPER_PATH . "{$helper}_helper.php";
}
}
Implementing Model
We will implement Model in the simplest way, by creating two class files:
Mysql.class.php - this class is under framework/database, it is to encapsulate database connection and some basic SQL query methods.
Model.class.php - this is the Base Model class, it contains methods for all kinds of CRUD
Copy Code<?php
/**
*================================================================
*framework/database/Mysql.class.php
*Database operation class
*================================================================
*/
class Mysql{
protected $conn = false; //DB connection resources
protected $sql; //sql statement
/**
* Constructor, to connect to database, select database and set charset
* @param $config string configuration array
*/
public function __construct($config = array()){
$host = isset($config['host'])? $config['host'] : 'localhost';
$user = isset($config['user'])? $config['user'] : 'root';
$password = isset($config['password'])? $config['password'] : '';
$dbname = isset($config['dbname'])? $config['dbname'] : '';
$port = isset($config['port'])? $config['port'] : '3306';
$charset = isset($config['charset'])? $config['charset'] : '3306';
$this->conn = mysql_connect("$host:$port",$user,$password) or die('Database connection error');
mysql_select_db($dbname) or die('Database selection error');
$this->setChar($charset);
}
/**
* Set charset
* @access private
* @param $charset string charset
*/
private function setChar($charest){
$sql = 'set names '.$charest;
$this->query($sql);
}
/**
* Execute SQL statement
* @access public
* @param $sql string SQL query statement
* @return $result，if succeed, return resrouces; if fail return error message and exit
*/
public function query($sql){
$this->sql = $sql;
// Write SQL statement into log
$str = $sql . " [". date("Y-m-d H:i:s") ."]" . PHP_EOL;
file_put_contents("log.txt", $str,FILE_APPEND);
$result = mysql_query($this->sql,$this->conn);
if (! $result) {
die($this->errno().':'.$this->error().'<br />Error SQL statement is '.$this->sql.'<br />');
}
return $result;
}
/**
* Get the first column of the first record
* @access public
* @param $sql string SQL query statement
* @return return the value of this column
*/
public function getOne($sql){
$result = $this->query($sql);
$row = mysql_fetch_row($result);
if ($row) {
return $row[0];
} else {
return false;
}
}
/**
* Get one record
* @access public
* @param $sql SQL query statement
* @return array associative array
*/
public function getRow($sql){
if ($result = $this->query($sql)) {
$row = mysql_fetch_assoc($result);
return $row;
} else {
return false;
}
}
/**
* Get all records
* @access public
* @param $sql SQL query statement
* @return $list an 2D array containing all result records
*/
public function getAll($sql){
$result = $this->query($sql);
$list = array();
while ($row = mysql_fetch_assoc($result)){
$list[] = $row;
}
return $list;
}
/**
* Get the value of a column
* @access public
* @param $sql string SQL query statement
* @return $list array an array of the value of this column
*/
public function getCol($sql){
$result = $this->query($sql);
$list = array();
while ($row = mysql_fetch_row($result)) {
$list[] = $row[0];
}
return $list;
}
/**
* Get last insert id
*/
public function getInsertId(){
return mysql_insert_id($this->conn);
}
/**
* Get error number
* @access private
* @return error number
*/
public function errno(){
return mysql_errno($this->conn);
}
/**
* Get error message
* @access private
* @return error message
*/
public function error(){
return mysql_error($this->conn);
}
}
Here is the Model.class.php
Copy Code<?php
// framework/core/Model.class.php
// Base Model Class
class Model{
protected $db; //database connection object
protected $table; //table name
protected $fields = array(); //fields list
public function __construct($table){
$dbconfig['host'] = $GLOBALS['config']['host'];
$dbconfig['user'] = $GLOBALS['config']['user'];
$dbconfig['password'] = $GLOBALS['config']['password'];
$dbconfig['dbname'] = $GLOBALS['config']['dbname'];
$dbconfig['port'] = $GLOBALS['config']['port'];
$dbconfig['charset'] = $GLOBALS['config']['charset'];
$this->db = new Mysql($dbconfig);
$this->table = $GLOBALS['config']['prefix'] . $table;
$this->getFields();
}
/**
* Get the list of table fields
*
*/
private function getFields(){
$sql = "DESC ". $this->table;
$result = $this->db->getAll($sql);
foreach ($result as $v) {
$this->fields[] = $v['Field'];
if ($v['Key'] == 'PRI') {
// If there is PK, save it in $pk
$pk = $v['Field'];
}
}
// If there is PK, add it into fields list
if (isset($pk)) {
$this->fields['pk'] = $pk;
}
}
/**
* Insert records
* @access public
* @param $list array associative array
* @return mixed If succeed return inserted record id, else return false
*/
public function insert($list){
$field_list = ''; //field list string
$value_list = ''; //value list string
foreach ($list as $k => $v) {
if (in_array($k, $this->fields)) {
$field_list .= "`".$k."`" . ',';
$value_list .= "'".$v."'" . ',';
}
}
// Trim the comma on the right
$field_list = rtrim($field_list,',');
$value_list = rtrim($value_list,',');
// Construct sql statement
$sql = "INSERT INTO `{$this->table}` ({$field_list}) VALUES ($value_list)";
if ($this->db->query($sql)) {
// Insert succeed, return the last record’s id
return $this->db->getInsertId();
//return true;
} else {
// Insert fail, return false
return false;
}
}
/**
* Update records
* @access public
* @param $list array associative array needs to be updated
* @return mixed If succeed return the count of affected rows, else return false
*/
public function update($list){
$uplist = ''; //update fields
$where = 0; //update condition, default is 0
foreach ($list as $k => $v) {
if (in_array($k, $this->fields)) {
if ($k == $this->fields['pk']) {
// If it’s PK, construct where condition
$where = "`$k`=$v";
} else {
// If not PK, construct update list
$uplist .= "`$k`='$v'".",";
}
}
}
// Trim comma on the right of update list
$uplist = rtrim($uplist,',');
// Construct SQL statement
$sql = "UPDATE `{$this->table}` SET {$uplist} WHERE {$where}";
if ($this->db->query($sql)) {
// If succeed, return the count of affected rows
if ($rows = mysql_affected_rows()) {
// Has count of affected rows
return $rows;
} else {
// No count of affected rows, hence no update operation
return false;
}
} else {
// If fail, return false
return false;
}
}
/**
* Delete records
* @access public
* @param $pk mixed could be an int or an array
* @return mixed If succeed, return the count of deleted records, if fail, return false
*/
public function delete($pk){
$where = 0; //condition string
//Check if $pk is a single value or array, and construct where condition accordingly
if (is_array($pk)) {
// array
$where = "`{$this->fields['pk']}` in (".implode(',', $pk).")";
} else {
// single value
$where = "`{$this->fields['pk']}`=$pk";
}
// Construct SQL statement
$sql = "DELETE FROM `{$this->table}` WHERE $where";
if ($this->db->query($sql)) {
// If succeed, return the count of affected rows
if ($rows = mysql_affected_rows()) {
// Has count of affected rows
return $rows;
} else {
// No count of affected rows, hence no delete operation
return false;
}
} else {
// If fail, return false
return false;
}
}
/**
* Get info based on PK
* @param $pk int Primary Key
* @return array an array of single record
*/
public function selectByPk($pk){
$sql = "select * from `{$this->table}` where `{$this->fields['pk']}`=$pk";
return $this->db->getRow($sql);
}
/**
* Get the count of all records
*
*/
public function total(){
$sql = "select count(*) from {$this->table}";
return $this->db->getOne($sql);
}
/*