An article detailing the principles of the PHP template engine (with code examples)

Developing a web project is usually divided into two parts. One part is GUI, that is, interface and art, written using HTML, CSS, JS, and the other part is business logic, that is, programs and functions, written using PHP. The template engine is the "bridge" that connects the two parts. It can be understood as a PHP class, which defines many methods to load the original output of PHP into the interface style and then output it.

The code written before using the template is like this:

In this way, there is no separation between art and logic. Simply put, PHP programmers must not only write programs but also be proficient in art. This It is often very difficult, so the two parts of the work need to be separated.

Let’s create a simple template engine as an example to better understand the principles of the template engine.

As mentioned before, developing a web project is divided into two parts: GUI and business logic, so we create two folders, one named "templates", which stores templates, create a new tpl.html file, and name the other For "PHP", which stores business logic, create a new index.php file.

tpl.html file code usually looks like this:

<{ $content;}>

It can be seen that compared with the previous code, tpl.html only has html code and no php code, but new ones have been added Tags, this type of tag is defined by yourself, and the content inside can only be recognized after being compiled by the template engine. The compiled files are stored in the "templates_c" folder. This file is mainly used for interface design, and will use a large number of CSS, JS and other technologies.

At this time, tpl.html and index.php are still separated and do not interfere with each other, so they need a "bridge" connection, that is, the template engine, which is actually a PHP class, so a mytpl can be created here. PHP file class.php.

The mytpl.class.php file usually defines a class MyTpl. An array tpl_var[] needs to be defined in the class to store the parameters of the custom content tag in tpl.html. In addition, some methods need to be defined. These methods The main purpose is to convert unrecognized content tags in tpl.hml into PHP statements, and then write them to tpl_c.html in a "templates_c" folder. This process is called compilation.

Usually the code of the tpl_c.html file is like this: