//wordpressのメソッドをロード
    require_once($_SERVER['DOCUMENT_ROOT'] . '/blog/wp-load.php');

    $args = array(
      'post_type'   => 'post',
      'post_status' => 'publish',
    );

    //記事を取得するためにWordPressのクラスをnewする
    $the_query = new WP_Query($args);
    ↑ここでエラーになる

[2020-05-29 15:54:38] front.ERROR [st58voktkdac0kv7bg4i4nh5gk] [8d90b70] [anon.] [Eccube\Log\Logger:log:66] - システムエラーが発生しました。 ["Attempted to load class \"WP_Query\" from namespace \"Eccube\\Controller\".\nDid you forget a \"use\" statement for another namespace?","/Users/Haru/GoogleDrive/works/external_matters/user/example/source/www/public_html/src/Eccube/Controller/ProductController.php",270,"#0 /Users/Haru/GoogleDrive/works/external_matters/user/example/source/www/public_html/vendor/symfony/http-kernel/HttpKernel.php(151): Eccube\\Controller\\ProductController->detail(Object(Symfony\\Component\\HttpFoundation\\Request), Object(Eccube\\Entity\\Product))\n#1 /Users/Haru/GoogleDrive/works/external_matters/user/example/source/www/public_html/vendor/symfony/http-kernel/HttpKernel.php(68): Symfony\\Component\\HttpKernel\\HttpKernel->handleRaw(Object(Symfony\\Component\\HttpFoundation\\Request), 1)\n#2 /Users/Haru/GoogleDrive/works/external_matters/user/example/source/www/public_html/vendor/symfony/http-kernel/Kernel.php(200): Symfony\\Component\\HttpKernel\\HttpKernel->handle(Object(Symfony\\Component\\HttpFoundation\\Request), 1, true)\n#3 /Users/Haru/GoogleDrive/works/external_matters/user/example/source/www/public_html/index.php(76): Symfony\\Component\\HttpKernel\\Kernel->handle(Object(Symfony\\Component\\HttpFoundation\\Request))\n#4 {main}"] [GET, /products/detail/3, ::1, http://example:8888/, Mozilla/5.0 (Macintosh; Intel Mac OS X 10_13_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/81.0.4044.138 Safari/537.36]