How to create a PHP function library and make it support dependency injection?

How to create a PHP function library that supports dependency injection (DI): Create a Composer package as a function library. Implement function library functions, such as implementing a greeting function in a file. Install the PhpDI container and create a container configuration, adding the function library class as a factory definition to the container. Use libraries in code and inject dependencies, such as using containers to obtain instances of library classes. In practical applications, such as saving user data to the database, injecting database connections to improve flexibility.

How to create a PHP function library and make it support dependency injection

Introduction

Function library is a powerful tool for code reuse in PHP. By using dependency injection (DI), you can write more flexible, testable libraries. This article will show you how to create and use a DI-enabled PHP function library.

Create a function library

First, you need to create a Composer package as your function library. Using the composer package manager, create a new package by running the following command:

composer init

Fill in the package information and then run the following command to install the Composer autoloader:

composer install

Now, in your project Create a new directory to use as the library code. For example:

php
└── vendor
└── my-library
    └── src
        └── FunctionLibrary.php

Implement the function library

In FunctionLibrary.php, implement the function library function. For example:

namespace MyLibrary;

class FunctionLibrary
{
    public function greet(string $name): string
    {
        return "Hello, $name!";
    }
}

Configuring Dependency Injection

To support DI, you need to use a container to resolve dependencies. This article will use the PhpDI container.

Install PhpDI in your library package:

composer require php-di/phpdi

Next, create a container configuration in src/config.php:

$containerBuilder = new \DI\ContainerBuilder();
$containerBuilder->addDefinitions([
    'MyLibrary\FunctionLibrary' => \DI\factory(function () {
        return new FunctionLibrary();
    })
]);

$container = $containerBuilder->build();

Using function libraries

Now you can use your function library in your code and inject dependencies:

use MyLibrary\FunctionLibrary;
use DI\Container;

$container = new Container();

$functionLibrary = $container->get(FunctionLibrary::class);

echo $functionLibrary->greet('John'); // 输出：Hello, John!

Practical example

Suppose you have a library that saves user data to a database. You can make your library more flexible and testable by injecting the database connection in dependency injection:

namespace MyLibrary;

class UserRepository
{
    private $connection;

    public function __construct(\PDO $connection)
    {
        $this->connection = $connection;
    }

    public function persist(User $user): void
    {
        // 保存用户到数据库
    }
}

Then, add the following definition in the container configuration:

$containerBuilder->addDefinitions([
    \PDO::class => \DI\factory(function () {
        return new \PDO('mysql:host=localhost;dbname=my_database', 'username', 'password');
    }),
    'MyLibrary\UserRepository' => \DI\factory(function (Container $container) {
        return new UserRepository($container->get(\PDO::class));
    })
]);

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