In the previous  chapter, we learned about some of the plug-in functions that allow us to  output new content anywhere in the site. In this chapter, we'll learn  about the built-in functions of several systems to help make things  easier.

In the last chapter we have exposed a built-in function "add", which is called in the plugin class: $ this-> add (). The built-in function is to achieve the output of the html code.

A practical example is：

$this->add($params,'home_top',$data);

This has been learned in the previous chapter.

Next we will introduce a few useful built-in functions：

1、"Set" function

Set function is  stored as a key-value pair, for example, we want to store the variable a  in the storage space of the key b, then we can call the set function：

$this->set(b,a);

Practical, for example, we have to open up a plug-in storage space, then you can use the following code：

    public function open(&$params)
    {
        $this->set($this->plugin.'_announcement', '');
    }

We opened up a key named "$ this->plugin. '_ announcement'" storage space, the initial space is empty.

The suggested  key names are in the form of "plugin name_variables", as in the example  above for "$ this-> plugin. '_ announcement'", $ this-> plugin is  the plugin name we defined.

2、"Get" function

Get function is used to take out the contents of the storage, only one parameter, is the key name. Then the above example, we now want to take out the key storage space b content, we can do：

$this->get(b)

With the announcement plug-in example, is：

$this->get($this->plugin.'_announcement')

3、"Delete" function

Delete function is used to delete the key storage space. When  you are sure you do not need to use the development of the key space,  you can delete it, so as not to create too much garbage. This is normally used when closing plug-ins. For example, when you close the announcement plug-in, we use the function to clear the announcement of storage space：

    public function close(&$params)
    {
        $this->delete($this->plugin.'_announcement');
    }

Use is very simple, on a parameter, the parameter is "set" function to set the key name.

With these four built-in functions, we can design a lot of plug-in effects you want to achieve.

You can find the bulletin plugin file, and then refer to the code.