【NextAuth】Credentials ProviderでシンプルなID/パスワード認証システム

DATABASE_URL="mysql://ユーザー名:パスワード@ホスト:3306/データベース名"

npm install next-auth

import NextAuth from "next-auth";
import CredentialsProvider from "next-auth/providers/credentials";

const handler = NextAuth({
  providers: [
    CredentialsProvider({
      name: "Email & Password",
      credentials: {
        email: { 
          label: "メールアドレス", 
          type: "email",
          placeholder: "email@example.com"
        },
        password: { 
          label: "パスワード", 
          type: "password" 
        }
      },
      async authorize(credentials) {
        try {
          // PHP APIを呼び出してユーザー認証
          const res = await fetch("https://あなたのドメイン/auth-api.php", {
            method: 'POST',
            body: JSON.stringify({
              email: credentials?.email,
              password: credentials?.password
            }),
            headers: { "Content-Type": "application/json" }
          });

          const user = await res.json();

          if (user.success) {
            return {
              id: user.data.id,
              name: user.data.name,
              email: user.data.email
            }
          }
          return null;
          
        } catch (error) {
          console.error("Auth Error:", error);
          return null;
        }
      }
    })
  ],
//  pages: {
//    signIn: '/auth/signin',  // カスタムログインページのパス
//  }
});

export { handler as GET, handler as POST };

<?php
header('Content-Type: application/json');
header('Access-Control-Allow-Origin: *');
header('Access-Control-Allow-Methods: POST');
header('Access-Control-Allow-Headers: Content-Type');

// POSTデータの取得
$json = file_get_contents('php://input');
$data = json_decode($json, true);

// データベース接続情報
$host = 'xxxx';
$dbname = 'xxxx';
$user = 'xxxx';
$pass = 'xxxx';

try {
    $pdo = new PDO("mysql:host=$host;dbname=$dbname", $user, $pass);
    $stmt = $pdo->prepare('SELECT * FROM users WHERE email = ? AND password = ? LIMIT 1');
    $stmt->execute([$data['email'], $data['password']]);
    $user = $stmt->fetch(PDO::FETCH_ASSOC);

    if ($user) {
        echo json_encode([
            'success' => true,
            'data' => [
                'id' => $user['id'],
                'email' => $user['email'],
                'name' => $user['name']
            ]
        ]);
    } else {
        echo json_encode([
            'success' => false,
            'error' => 'Invalid credentials'
        ]);
    }
} catch(PDOException $e) {
    echo json_encode([
        'success' => false,
        'error' => $e->getMessage()
    ]);
}
?>