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This article mainly explains "how to parse and render the view template engine through PHP". The content in the article is simple and clear, and it is easy to learn and understand. Please follow the editor's train of thought to study and learn "how to parse and render the view template engine through PHP".

0. Introduction

In the previous tutorial, the Academy gave you a brief introduction to what the MVC design pattern is, and demonstrated how to write a simple HTTP controller based on native PHP code, which corresponds to C (Controller) in MVC mode. Today, let's take a look at another module in MVC pattern-View (View, corresponding to V in MVC pattern), and implement a simple view template engine based on native PHP code.

Before this, our view rendering implementation is relatively simple and rough, that is, the corresponding PHP view template is introduced directly through the include statement, and then the variables valid in the current scope will take effect in the introduced view template. Take the home page of the blog application as an example, the corresponding view introduction code is as follows (the code is in HomeController.php):

Public function index ()

{

$albums = $this- > connection- > table ('albums')-> selectAll ()

$pageTitle = $siteName = $this- > container- > resolve ('app.name')

$siteUrl = $this- > container- > resolve ('app.url')

$siteDesc = $this- > container- > resolve ('app.desc')

Include _ _ DIR__. "/.. / views/home.php"

}

The variables set in the current controller method can be used directly in the home.php view template, because the essence of include is to import the corresponding PHP script to the current location.

In PHP, the reason why HTML views can be rendered in this way is that PHP scripts and HTML documents can be mixed-programmed. PHP itself is regarded as a view template engine, and does not need to be like other languages (such as Java, Go, Python). It is necessary to introduce additional view template languages to dynamically introduce variables into HTML documents for rendering.

Although PHP Ecology also provides many third-party extension packs as independent view template engines to build more complex applications in an engineering way, such as Smarty, twig, Blade, etc., in order to simplify the system, we directly use PHP itself as the template language for HTML views.

However, in order to make the above view rendering implementation code more elegant, easy to maintain and extend, we refactored it in object-oriented code and adjusted it to support other template engines.

1. Write the PHP view engine implementation code

We create a new view subdirectory under the app directory to save the view template parsing and rendering related code, and then create a new engine subdirectory under the view directory to save the view template engine code.

Create a new ViewEngine interface under the engine directory as a contract for all PHP template engine implementations:

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