Detailed explanation of how Laravel applications connect to databases

In Laravel, connecting to the database is a very important thing, because it is the data storage and management center of our application. In this article, we will explain in detail how to connect a Laravel application to a database.

Step 1: Create a database in your database

First, create a database in your MySQL or MariaDB database server. In this example, we will create a database called "laravel_demo".

You can use MySQL's "CREATE DATABASE" statement to create a new database:

CREATE DATABASE laravel_demo;

Step 2: Configure the database

In this step, we need to create a new database in Laravel Define the database connection. Laravel uses .env files by default to configure applications, so you can add the following database connection information in the .env file:

DB_CONNECTION=mysql
DB_HOST=127.0.0.1
DB_PORT=3306
DB_DATABASE=laravel_demo
DB_USERNAME=your_db_username
DB_PASSWORD=your_db_password

In this example, we used MySQL as our database server and locally The default port 3306 is used on the host. We also set the database name to "laravel_demo" and defined the username and password for the database connection.

Step 3: Run Database Migration

Once you have configured your database connection, you can run Laravel's database migration to create data tables and fields. Laravel's database migration is an automated database management mechanism that allows you to manage database schema changes in your application.

To run database migrations, go into your Laravel application directory in the terminal and run the following command:

php artisan migrate

This will cause Laravel to execute the migration files in the app/database/migrations directory.

Step 4: Use Eloquent ORM

Laravel provides a very convenient ORM (Object-Relational Mapping, Object Relational Mapping) implementation, which is called Eloquent. This allows you to use PHP model classes to represent database tables and use model instances to perform database operations.

In this example, assuming we have created a "users" table, you can access it by creating a model named "User":

php artisan make:model User

Running this command will Create a new model named "User" in the application. Now, you can use this in your controller to perform various database operations:

<?php  
namespace App\Http\Controllers;
 
use App\User;
use Illuminate\Http\Request;
 
class UserController extends Controller
{
    public function index()
    {
        // 列出所有用户
        $users = User::all();
 
        // 渲染视图并传递用户数据
        return view(&#39;users&#39;, [&#39;users&#39; => $users]);
    }
 
    public function create(Request $request)
    {
         // 创建一个新用户
         $user = new User;
         $user->name = $request->name;
         $user->email = $request->email;
         $user->save();
 
         return redirect('/users');
    }
 
    public function delete(User $user)
    {
         // 删除指定用户
         $user->delete();
 
         return redirect('/users');
    }
}

In the above example, we are using Eloquent ORM to get all users, create new users, and delete existing users. It should be noted that we did not use any native SQL query statements in these operations, but used the advanced query syntax provided by Eloquent.

Step 5: Handle connection errors

It is not uncommon for errors to occur when connecting to the database. If you find an error when connecting to the database, you can check Laravel's logs to understand the problem.

Laravel places logs in the storage/logs/laravel.log file by default. In addition, you can also write logs by using the Log class in your controller or model:

use Illuminate\Support\Facades\Log;
 
Log::debug('连接数据库时发生错误：' . $exception->getMessage());

In this example, we use Laravel's logging mechanism to record errors that occur when connecting to the database .

Conclusion

Laravel is a powerful and easy-to-use PHP framework that provides many database-related features and tools. Connecting the Laravel application to the database is an important step, which requires us to define and configure the database connection information in the Laravel application, and use Eloquent ORM to operate the database. Of course, in actual development work, you also need to know how to deal with connection errors and other common problems. Hope this article can help you understand how to connect Laravel to the database.

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