我通過functions.php 設置了一個wordpress 站點，以將SMTP 與PHPMailer 結合使用（下面的代碼片段）。add_action( 'phpmailer_init', 'setup_phpmailer_init' );function setup_phpmailer_init( PHPMailer $phpmailer ) {    $phpmailer->Host = 'HOSTNAME'; // for example, smtp.mailtrap.io    $phpmailer->Port = 587; // set the appropriate port: 465, 2525, etc.    $phpmailer->Username = 'YOURUSERNAME'; // your SMTP username    $phpmailer->Password = 'YOURPASSWORD'; // your SMTP password    $phpmailer->SMTPAuth = true;     $phpmailer->SMTPSecure = 'tls'; // preferable but optional    $phpmailer->IsSMTP();除了 WooCommerce 之外，這對所有內容都沒有問題。WooCommerce 無法發送電子郵件，并出現以下錯誤：2020-08-18T00:36:33+00:00 CRITICAL Uncaught TypeError: Argument 1 passed to setup_phpmailer_init() must be an instance of PHPMailer, instance of PHPMailer\PHPMailer\PHPMailer given, called in PathToWordpress/web/wp/wp-includes/class-wp-hook.php on line 287 and defined in PathToWordpress/web/app/themes/theme-name/functions.php:362Stack trace:#0 PathToWordpress/web/wp/wp-includes/class-wp-hook.php(287): setup_phpmailer_init()#1 PathToWordpress/web/wp/wp-includes/class-wp-hook.php(311): WP_Hook->apply_filters()#2 PathToWordpress/web/wp/wp-includes/plugin.php(544): WP_Hook->do_action()#3 PathToWordpress/web/wp/wp-includes/pluggable.php(494): do_action_ref_array()#4 PathToWordpress/web/app/plugins/woocommerce/includes/class-wc-emails.php(650): wp_mail()#5 PathToWordpress/web/wp/wp-includes/class-wp-hook.php(287): WC_Emails->no_stock()#6 PathToWordpress/web/wp/wp-includes/class-wp-hook.php(311): WP_Hook->apply in PathToWordpress/web/app/themes/theme-name/functions.php on line 362可能是什么原因導致此錯誤？