Example of php implementing mvc mode

{some_text}
{some_more_text}

They have no meaning in the documentation, all they mean is PHP will replace it with something else.

If you agree with this loose description of views, you will also agree that most template solutions do not effectively separate views and models. The template tag will be replaced with whatever is stored in the model.

Ask yourself a few questions when you implement the view: "Is it easy to replace the entire view?" "How long does it take to implement a new view?" "Is it easy to replace the view's description language? (For example, using SOAP document replaces HTML document)"

2. Model

Model represents program logic. (Often called the business layer in enterprise-level programs)

In general, the task of the model is to convert the original data into data containing certain meanings, which will be displayed by the view. Typically, the model will encapsulate data queries, perhaps through some abstract data class (data access layer) to implement the query. For example, if you wish to calculate the annual rainfall in the UK (just to find yourself a nice holiday spot), the model will receive the daily rainfall for ten years, calculate the average, and pass it to the view.

3. Controller

Simply put, the controller is the first part called by the incoming HTTP request in the web application. It checks the received request, such as some GET variables, and makes appropriate feedback. It's difficult to start writing other PHP code until you write your first controller. The most common usage is a structure like a switch statement in index.php:

switch ($_GET['viewpage']) {
case "news":
$page=new NewsRenderer;
break;
case "links":
$page=new LinksRenderer ;
break;
default:
$page=new HomePageRenderer;
break;
}
$page->display();
?>

This code mixes process-oriented and Object's code, but for small sites this is usually the best option. Although the above code can still be optimized. Controllers are actually controls used to trigger bindings between the model's data and view elements.

Here is a simple example using MVC pattern. First we need a database access class, which is an ordinary class.

/**
* A simple class for querying MySQL
*/
class DataAccess {
/**
* Private
* $db stores a database resource
*/
var $db;
/**
* Private
* $query stores a query resource
* /
var $query; // Query resource
//! A constructor.
/**
* Constucts a new DataAccess object
* @param $host string hostname for dbserver
* @param $user string dbserver user
* @param $pass string dbserver user password
* @param $db string database name
*/
function DataAccess ($host,$user,$pass,$db) {
$this->db=mysql_pconnect($host,$user,$pass);
mysql_select_db($db,$this->db);
}
//! An accessor
/**
* Fetches a query resources and stores it in a local member
* @param $sql string the database query to run
* @return void
*/
function fetch($sql) {
$this->query=mysql_unbuffered_query($sql,$this->db); // Perform query here
} p>
//! An accessor
/**
* Returns an associative array of a query row
* @return mixed
*/
function getRow () {
if ( $row=mysql_fetch_array($this->query,MYSQL_ASSOC) )
return $row;
else
return false;
}
}
?>

Put the model on top of it.

/**
* Fetches "products" from the database
* link: http://bbs.it-home.org
*/
class ProductModel {
/**
* Private
* $dao an instance of the DataAccess class
*/
var $dao;
//! A constructor.
/**
* Constucts a new ProductModel object
* @param $dbobject an instance of the DataAccess class
*/
function ProductModel (&$dao) {
$this->dao=& $dao;
}
 //! A manipulator
/**
* Tells the $dboject to store this query as a resource
* @param $start the row to start from
* @param $rows the number of rows to fetch
* @return void
*/
function listProducts($start=1,$rows=50) {
$this->dao->fetch("SELECT * FROM products LIMIT ".$ start.", ".$rows);
}
//! A manipulator
/**
* Tells the $dboject to store this query as a resource
* @param $id a primary key for a row
* @return void
*/
function listProduct($id) {
$this-> dao->fetch("SELECT * FROM products WHERE PRODUCTID='".$id."'");
}
//! A manipulator
/**
* Fetches a product as an associative array from the $dbobject
* @return mixed
* /
function getProduct() {
if ( $product=$this->dao->getRow() )
return $product;
else
return false;
}
}
?>
 > ;

Note: Between the model and the data access class, their interaction is never more than one line - no multiple lines are sent, which can quickly slow down the program. For the same program that uses schema classes, it only needs to keep one row (Row) in memory - the rest is given to the saved query resource (query resource) - in other words, we let MYSQL keep the results for us.

Next is the view (the following code removes the html content).

/**
* Binds product data to HTML rendering
* link：http://bbs.it-home.org
*/
class ProductView {
/**
* Private
* $model an instance of the ProductModel class
*/
var $model;
/**
* Private
* $output rendered HTML is stored here for display
*/
var $output;
//! A constructor.
/**
* Constucts a new ProductView object
* @param $model an instance of the ProductModel class
*/
function ProductView (&$model) {
 $this->model=& $model;
}
//! A manipulator
/**
* Builds the top of an HTML page
* @return void
*/
function header () {
< ;p>}
//! A manipulator
/**
* Builds the bottom of an HTML page
* @return void
*/
function footer () {

}
//! A manipulator
/**
* Displays a single product
* @return void
*/
function productItem($id=1) {
$this->model->listProduct($id);
while ( $product =$this->model->getProduct() ) {
// Bind data to HTML
}
}
//! A manipulator
/**
* Builds a product table
* @return void
*/
function productTable($rownum=1) {
$rowsperpage='20';
$this->model->listProducts($rownum,$rowsperpage);
while ( $product=$this->model- >getProduct() ) {
// Bind data to HTML
}
}
//! An accessor
/**
* Returns the rendered HTML
* @return string
*/
function display () {
return $this->output;
}
}
?>

Finally the controller, we will implement the view as a subclass. A constructor.

/**

ProductView::ProductView($model);
$this->header();
switch ( $getvars['view'] ) {
case "product":
$this->productItem($getvars['id']);
break;
default:
if ( empty ($getvars['rownum']) ) {
$this-> ;productTable();
} else {
$this->productTable($getvars['rownum']);
}
break;
}
$this->footer();
}
}
?> ;




Copy code


Note: This is not the only way to implement MVC - for example, you can use controllers to implement models and integrate views at the same time. This is just one way to demonstrate the pattern.
The index.php file looks like this:






require_once('lib/DataAccess.php');

$productModel =& new ProductModel($dao);

$productController=& new ProductController($productModel,$_GET);

echo $productController->display();

Copy code


There are some tricks for using controllers, in PHP you can do this:
$this->{$_GET['method']}($_GET['param']);
It is recommended to define the namespace form of the program URL, so that it will be more standardized, such as:





"index.php?class=ProductView&method=productItem&id=4"

$view->{$_GET['method']($_GET['id']);

Sometimes building a controller is not an easy task, such as when there is a trade-off between development speed and adaptability. A good place to get inspiration is the Apache group's Java Struts, whose controllers are entirely defined by XML documents.