How to use decorator pattern in PHP?

The decorator pattern allows you to dynamically add functionality without modifying the original object, by creating a wrapper class. Extra functionality can be easily added by wrapping decorators around existing objects. Decorator patterns can be used in combination, and the operation can be reversed by removing the decorator to achieve flexible object function expansion.

Decorator pattern in PHP

In PHP, the decorator pattern is a design pattern that allows Dynamically add new functionality to the object without the original object. This is accomplished by creating a wrapper class that attaches itself to the original object and provides additional functionality.

Practical example: Adding tags to user input string

Consider the following scenario: We have a class for creating HTML tags, but we need a way to dynamically add tags to user-entered strings. We can use the decorator pattern to achieve this functionality:

<?php
// 创建标签包装器类
class TagDecorator
{
    protected $tag;
    protected $object;

    public function __construct($tag, $object)
    {
        $this->tag = $tag;
        $this->object = $object;
    }

    public function __toString()
    {
        return "<{$this->tag}>{$this->object}</{$this->tag}>";
    }
}

// 创建原始对象
$input = 'Hello, world!';

// 使用包装器类添加标签
$boldDecorator = new TagDecorator('b', $input);
$italicDecorator = new TagDecorator('i', $boldDecorator);

// 显示带标签的字符串
echo $italicDecorator;

// 输出：
// <b><i>Hello, world!</i></b>
?>

In this example, the TagDecorator class is a wrapper that appends a tag to the original input string. By wrapping a decorator around an existing object, we can easily add additional functionality without affecting the original object's code.

Note:

• The decorator class should implement the same interface as the wrapping object or inherit from the wrapping object.
• Decorator patterns can be easily combined to create objects with complex functionality.
• Decorators can be reversible, allowing functionality to be removed when needed.

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