【Laravel】クエリパラメータ付きURLのABテストをおこなう際の注意点

php artisan make:middleware AbTestRedirect

<?php

namespace App\Http\Middleware;

use Closure;
use Illuminate\Http\Request;

class AbTestRedirect
{
    /** @var array ABテストパターン */
    private const AB_TEST_PATTERNS = [
        [
            'test_name' => 'top_ab_test',
            'target_path' => '/page-a',
            'redirect_path_b' => '/page-b',
            'cookie_name' => 'top_ab_test_group',
        ],
    ];
    
    /**
     * Handle an incoming request.
     *
     * @param  \Illuminate\Http\Request  $request
     * @param  \Closure(\Illuminate\Http\Request): (\Illuminate\Http\Response|\Illuminate\Http\RedirectResponse)  $next
     * @return \Illuminate\Http\Response|\Illuminate\Http\RedirectResponse
     */
    public function handle(Request $request, Closure $next)
    {
        foreach (self::AB_TEST_PATTERNS as $test) {
            // 今のリクエストが対象か確認
            if (trim($request->path(), '/') === trim($test['target_path'], '/')) {
                $cookie_name = $test['cookie_name'];

                // グループ取得 or 新規割当
                $group = $request->cookie($cookie_name);
                if (!$group) {
                    $group = rand(0, 1) ? 'A' : 'B';
                    cookie()->queue(cookie($cookie_name, $group, 60 * 24 * 14)); // 14日間
                }

                // Bグループならリダイレクト
                if ($group === 'B') {
                    $queryString = $request->getQueryString();
                    $redirectUrl = $test['redirect_path_b'] . ($queryString ? '?' . $queryString : '');
                    return redirect($redirectUrl);
                }

                // Aグループ or cookieありならそのまま
                break; // 他のABテストは無視（1つのリクエストに対して1テストだけ適用）
            }
        }

        return $next($request);
    }
}

<?php

namespace App\Http;

use Illuminate\Foundation\Http\Kernel as HttpKernel;

class Kernel extends HttpKernel
{
    ... 

    /**
     * The application's route middleware.
     *
     * These middleware may be assigned to groups or used individually.
     *
     * @var array<string, class-string|string>
     */
    protected $routeMiddleware = [
        'auth' => \App\Http\Middleware\Authenticate::class,
        ... 
        'ab_test' => \App\Http\Middleware\AbTestRedirect::class,
    ];

Route::view('/page-a', 'page_a')->name('page_a')->middleware('ab_test');
Route::view('/page-b', 'page_b')->name('page_b');