A guide to choosing PHP design patterns

Guidelines for Choosing PHP Design Patterns

A design pattern is a predefined solution to common programming problems. They are designed to improve code reusability, scalability, and maintainability.

Principles for selecting design patterns

• Problem domain: Design patterns map to specific problem domains.
• Code duplication: Design patterns help reduce code duplication.
• Extensibility: Design patterns make the code easier to extend or modify.
• Maintainability: Design patterns improve the maintainability of code, making it easy to read and understand.

Common PHP design patterns

Creative

• Factory method: Create an object without specifying the specific class of the object.
• Single case mode: Ensure that a class can only have one instance.
• Builder Mode: Create complex objects step by step and easy to customize.

Structural

• Adapter pattern: Enables incompatible objects to work together.
• Bridge mode: Separate the abstract part from the implementation part to improve scalability.
• Combined mode: Group objects into a tree structure to represent the part-whole hierarchy.

Behavioral

• Strategy mode: Change certain behaviors of the object based on different algorithms or strategies.
• Observer mode: When the subject state changes, the observer will automatically receive a notification.
• Chain of responsibility mode: Process the request along the chain of responsibility until an object can handle it.

Practical case: singleton mode

Suppose you are creating an e-commerce website and need a logging class responsible for writing log files. To ensure that there is only one log file, you can use the singleton mode:

class Logger
{
    private static $instance;
    private $handle;

    private function __construct()
    {
        $this->handle = fopen('log.txt', 'a');
    }

    public static function getInstance()
    {
        if (!isset(self::$instance)) {
            self::$instance = new Logger();
        }
        return self::$instance;
    }

    public function write($message)
    {
        fwrite($this->handle, $message . "\n");
    }

    public function close()
    {
        fclose($this->handle);
    }
}

// 使用单例类
$logger = Logger::getInstance();
$logger->write('商品添加成功');
$logger->close();

Using the singleton mode, no matter how many requests there are in the website, there is always only one instance of the log file.

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