当新帖子/页面待处理时向管理员发送电子邮件通知

你是对的，它似乎与你链接的古腾堡问题直接相关。（在该线程中回答的原因https://github.com/WordPress/gutenberg/issues/15094#issuecomment-558986406）。

本质上，如果您使用一个插件将自定义元数据添加到启用了 Gutenberg 的帖子，则挂钩会被触发两次以实现向后兼容性，以确保无法使用 Gutenberg REST 调用的插件仍然可以保存其数据。

为了让你的案例工作，你必须向你的脚本添加条件检查，以确保你在正确的传递上运行它（即非Rest 调用）

add_action( 'transition_post_status', 'pending_submission_notifications_send_email', 10, 3 );
function pending_submission_notifications_send_email( $new_status, $old_status, $post ) {

    // If this is running in the Gutenberg REST call, ignore it
    if ( defined( 'REST_REQUEST' ) && REST_REQUEST ) { return false; }

    // Notify Admin that Contributor has written a post.
    if ( 'pending' === $new_status && user_can( $post->post_author, 'edit_posts' ) && ! user_can( $post->post_author, 'publish_posts' ) ) {
        $pending_submission_email = '[email protected]';
        $admins                   = ( empty( $pending_submission_email ) ) ? get_option( 'admin_email' ) : $pending_submission_email;
        $edit_link                = get_edit_post_link( $post->ID, '' );
        $preview_link             = get_permalink( $post->ID ) . '&preview=true';
        $username                 = get_userdata( $post->post_author );
        $username_last_edit       = get_the_modified_author();
        $subject                  = __( 'New post or page pending review', 'pending-submission-notifications' ) . ': "' . $post->post_title . '"';
        $message                  = __( 'A new post or page is pending review.', 'pending-submission-notifications' );
        $message                 .= "\r\n\r\n";
        $message                 .= __( 'Author', 'pending-submission-notifications' ) . ': ' . $username->user_login . "\r\n";
        $message                 .= __( 'Title', 'pending-submission-notifications' ) . ': ' . $post->post_title . "\r\n";
        $message                 .= "\r\n\r\n";
        $message                 .= __( 'Edit the submission', 'pending-submission-notifications' ) . ': ' . $edit_link . "\r\n";
        $message                 .= __( 'Preview the submission', 'pending-submission-notifications' ) . ': ' . $preview_link;
        $result                   = wp_mail( $admins, $subject, $message );
    } // Notify Contributor that Admin has published their post.
    elseif ( 'pending' === $old_status && 'publish' === $new_status && user_can( $post->post_author, 'edit_posts' ) && ! user_can( $post->post_author, 'publish_posts' ) ) {
        $username = get_userdata( $post->post_author );
        $url      = get_permalink( $post->ID );
        $subject  = __( 'Your submission is now live! ', 'pending-submission-notifications' );
        $message  = '"' . $post->post_title . '" ' . __( 'was just published ', 'pending-submission-notifications' ) . "! \r\n\r\n";
        $message .= $url;
        $result   = wp_mail( $username->user_email, $subject, $message );
    }
}

请记住，这是未经测试的，但根据上面链接的问题报告，这应该忽略通过古腾堡编辑器的第一次传递，只传递具有正确帖子数据的版本。