環境

% php artisan -V
Laravel Framework 10.30.1
% php -v
PHP 8.2.10 (cli) (built: Aug 31 2023 18:52:27) (NTS)
Copyright (c) The PHP Group
Zend Engine v4.2.10, Copyright (c) Zend Technologies
    with Zend OPcache v8.2.10, Copyright (c), by Zend Technologies

User

Users.php

<?php

namespace App\Models;

use Illuminate\Database\Eloquent\Factories\HasFactory;
use Illuminate\Database\Eloquent\Model;

# Classは処理のまとまりのこと、Modelはその処理の内容
class Users extends Model
{
    use HasFactory;

    public function Posts()
    {
# PostsというクラスがあることはPosts.phpに定義済み
        return $this->hasMany(Posts::class);
    }
}

2023_11_04_225616_create_users_table.php

<?php

use Illuminate\Database\Migrations\Migration;
use Illuminate\Database\Schema\Blueprint;
use Illuminate\Support\Facades\Schema;

return new class extends Migration
{
    /**
     * Run the migrations.
     */
    public function up(): void
    {
        Schema::create('users', function (Blueprint $table) {
            $table->id();
            $table->string('name');
            $table->string('email')->unique();
            $table->timestamp('email_verified_at')->nullable();
            $table->string('password');
            $table->rememberToken();
            $table->timestamps();
        });
    }

    /**
     * Reverse the migrations.
     */
    public function down(): void
    {
        Schema::dropIfExists('users');
    }
};

Post

Posts.php

<?php

namespace App\Models;

use Illuminate\Database\Eloquent\Factories\HasFactory;
use Illuminate\Database\Eloquent\Model;

# Classは処理のまとまりのこと、Modelはその処理の内容
class Posts extends Model
{
    use HasFactory;

    public function Users()
    {
        return $this->belongsTo(Users::class);
    }
}

2023_11_04_225632_create_posts_table.php


<?php

use Illuminate\Database\Migrations\Migration;
use Illuminate\Database\Schema\Blueprint;
use Illuminate\Support\Facades\Schema;
return new class extends Migration
{
    /**
     * Run the migrations.
     */
    public function up(): void
    {
        Schema::create('posts', function (Blueprint $table) {
            $table->id();
            $table->foreignId('user_id')
            ->references('id')
            ->on('users');
            $table->text('title');
            $table->text('subject');
            $table->timestamps();
        });
    }

    /**
     * Reverse the migrations.
     */
    public function down(): void
    {
        Schema::dropIfExists('posts');
    }
};

このようにファイルを作成し、"php artisan tinker"を実行。
users_idがuserのidとリレーションが出来ているのかを確認するとエラーが出てきた。

> $user = Users::find(18);
[!] Aliasing 'Users' to 'App\Models\Users' for this Tinker session.
= App\Models\Users {#6628
    id: 18,
    name: "斉藤 舞",
    email: "youichi.sasada@example.net",
    email_verified_at: null,
    password: "$2y$12$lDrHtpTiiB2rDtk7AnAWlesip3BVi.mg.2L4FK/jDjIJz2EHyAM76",
    remember_token: null,
    created_at: "2023-11-05 00:14:34",
    updated_at: "2023-11-05 00:14:34",
  }

> $user->Posts;

   Illuminate\Database\QueryException  SQLSTATE[42S22]: Column not found: 1054 Unknown column 'posts.users_id' in 'where clause' (Connection: mysql, SQL: select * from `posts` where `posts`.`users_id` = 18 and `posts`.`users_id` is not null).

下記のように修正するとリレーションを確認することが出来た。

Users.php

class Users extends Model
{
    use HasFactory;

    public function Posts()
    {
# PostsというクラスがあることはPosts.phpに定義済み
        return $this->hasMany(Posts::class, 'user_id');#", 'user_id'"を追加
    }
}

> $user->Posts;
= Illuminate\Database\Eloquent\Collection {#7248
    all: [
      App\Models\Posts {#6292
        id: 21,
        user_id: 20,
        title: "Hello",
        subject: "Occaecati quia quia ea explicabo similique voluptatem. Suscipit cumque repudiandae quia voluptas adipisci inventore doloribus. Aut cumque qui sed odit.",
        created_at: "2023-11-08 20:24:33",
        updated_at: "2023-11-08 20:24:33",
      },