What is the principle of mvc in php? Introduction to PHP's mvc implementation principle (with code)

Part of MVC in PHP is easy to understand. For example, M is the model model, which completes specific business logic; V is the view view, which is responsible for displaying information; C is the controller controller, which is responsible for issuing orders and executing methods. Distinguish, when the demand is transmitted from the front desk, determine what method to use to process it; then what is the implementation of the MVC principle in PHP? Let's use code to understand the MVC principle in depth.

1. File structure
Create 3 folders
controller folder stores controller files
view folder stores view files
model folder stores Data file
Create 1 index.php as the only entrance
2. Controller
We create a democontroller.php file in the controller folder. The file content is as follows

<?php 
class DemoController 
{ 
function index() 
{ 
echo(&#39;hello world&#39;); 
} 
} 
/* End of file democontroller.php */

In this file we just created an object named DemoController and contains an index method, which outputs hello world. Next, execute the index method in DemoController in index.php.
The code of index.php is as follows

<?php 
require(&#39;controller/democontroller.php&#39;); 
$controller=new DemoController(); 
$controller->index(); 
/* End of file index.php */

Run index.php, ok as expected we saw our long-lost hello world. These two files are very simple, but they also reveal a little bit of the essence of MVC, running the controller we want to run through the only entrance. Of course, the controller part should be determined by the uri, so let's rewrite index.php so that it can determine which controller to run through the uri.
index.php rewrite the code as follows:

<?php 
$c_str=$_GET[&#39;c&#39;]; 
//获取要运行的controller $c_name=$c_str.&#39;Controller&#39;; 
//按照约定url中获取的controller名字不包含Controller，此处补齐。 $c_path=&#39;controller/&#39;.$c_name.&#39;.php&#39;; 
//按照约定controller文件要建立在controller文件夹下，类名要与文件名相同，且文件名要全部小写。 $method=$_GET[&#39;a&#39;]; 
//获取要运行的action require($c_path); 
//加载controller文件 $controller=new $c_name; 
//实例化controller文件 $controller->$method(); 
//运行该实例下的action /* End of file index.php */

Enter http://localhost/index.php?c=demo&a=index in the browser and get our hello world. Of course, if we have another controller and want to run it, we only need to modify the values ​​of c and a in the url parameters.
There are several issues to explain here.
1. PHP is a dynamic language. We can directly use the string new to get the object we want and run the method we want, that is, the new above $c_name, we can understand it as new 'DemoController', because the value of $c_name itself is 'DemoController', of course, directly new Writing 'DemoController' like this is not possible. The 'DemoController' string must be transferred through a variable. The method is the same.
2. The value of c in our url is demo, which means $c_name The value should be demoController. Isn't PHP case-sensitive? Can it still run like this? The sentence "php is case-sensitive" is incomplete. In php, only variables (preceded by $) and constants (defined by define) are case-sensitive, while class names, method names and even some keywords are not case-sensitive. written. And true, false, null, etc. can only be all uppercase or all lowercase. Of course we'd better be case-sensitive during the actual encoding process.
3. View
We only output a "hello world" in the previous controller, which did not achieve the effect of mvc. Next, I will add the view function on this basis. I believe it will Here everyone can basically think of how to add the view function. Yes, it is achieved through the evil require or include.
First we create an index.php under the view folder and write anything (haha, I still wrote hello world). Then we rewrite our previous DemoController. The code is as follows:

<?php 
class DemoController 
{ 
function index() 
{ 
require(&#39;view/index.php&#39;); 
} 
} 
/* End of file democontroller.php */

Run it in the browser again to see if the content we want has been output.
Then we pass some data to the view through the controller. The code is as follows:

<?php 
class DemoController 
{ 
function index() 
{ 
$data[&#39;title&#39;]=&#39;First Title&#39;; 
$data[&#39;list&#39;]=array(&#39;A&#39;,&#39;B&#39;,&#39;C&#39;,&#39;D&#39;); 
require(&#39;view/index.php&#39;); 
} 
} 
/* End of file democontroller.php */

The index.php file code under the view folder is as follows:

<html> 
<head> 
<title>demo</title> 
</head> 
<body> 
<h1><?php echo $data[&#39;title&#39;];?></h1> 
<?php 
foreach ($data[&#39;list&#39;] as $item) 
{ 
echo $item.&#39;<br>&#39;; 
} 
?> 
</body> 
</html>

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