好的，这就是我最终的做法：对PHP函数的Ajax调用，该函数执行检查，其灵感来自this answer 并使用question I asked on StackOverflow. 重要的是，我确保只有在我们想要发布时才进行检查，这样就可以在不进行检查的情况下保存草稿。这最终是一个更容易的解决方案，可以真正阻止这篇文章的发表。它可能会帮助其他人，所以我把它写在这里。

首先，添加必要的Javascript：

//AJAX to validate event before publishing
//adapted from https://wordpress.stackexchange.com/questions/15546/dont-publish-custom-post-type-post-if-a-meta-data-field-isnt-valid
add_action(\'admin_enqueue_scripts-post.php\', \'ep_load_jquery_js\');   
add_action(\'admin_enqueue_scripts-post-new.php\', \'ep_load_jquery_js\');   
function ep_load_jquery_js(){
global $post;
if ( $post->post_type == \'event\' ) {
    wp_enqueue_script(\'jquery\');
}
}

add_action(\'admin_head-post.php\',\'ep_publish_admin_hook\');
add_action(\'admin_head-post-new.php\',\'ep_publish_admin_hook\');
function ep_publish_admin_hook(){
global $post;
if ( is_admin() && $post->post_type == \'event\' ){
    ?>
    <script language="javascript" type="text/javascript">
        jQuery(document).ready(function() {
            jQuery(\'#publish\').click(function() {
                if(jQuery(this).data("valid")) {
                    return true;
                }
                var form_data = jQuery(\'#post\').serializeArray();
                var data = {
                    action: \'ep_pre_submit_validation\',
                    security: \'<?php echo wp_create_nonce( \'pre_publish_validation\' ); ?>\',
                    form_data: jQuery.param(form_data),
                };
                jQuery.post(ajaxurl, data, function(response) {
                    if (response.indexOf(\'true\') > -1 || response == true) {
                        jQuery("#post").data("valid", true).submit();
                    } else {
                        alert("Error: " + response);
                        jQuery("#post").data("valid", false);

                    }
                    //hide loading icon, return Publish button to normal
                    jQuery(\'#ajax-loading\').hide();
                    jQuery(\'#publish\').removeClass(\'button-primary-disabled\');
                    jQuery(\'#save-post\').removeClass(\'button-disabled\');
                });
                return false;
            });
        });
    </script>
    <?php
}
}

add_action(\'wp_ajax_ep_pre_submit_validation\', \'ep_pre_submit_validation\');
function ep_pre_submit_validation() {
//simple Security check
check_ajax_referer( \'pre_publish_validation\', \'security\' );

//convert the string of data received to an array
//from https://wordpress.stackexchange.com/a/26536/10406
parse_str( $_POST[\'form_data\'], $vars );

//check that are actually trying to publish a post
if ( $vars[\'post_status\'] == \'publish\' || 
    (isset( $vars[\'original_publish\'] ) && 
     in_array( $vars[\'original_publish\'], array(\'Publish\', \'Schedule\', \'Update\') ) ) ) {
    if ( empty( $vars[\'_start_date\'] ) || empty( $vars[\'_end_date\'] ) ) {
        _e(\'Both Start and End date need to be filled\');
        die();
    }
    //make sure start < end
    elseif ( $vars[\'_start_date\'] > $vars[\'_end_date\'] ) {
        _e(\'Start date cannot be after End date\');
        die();
    }
    //check time is also inputted in case of a non-all-day event
    elseif ( !isset($vars[\'_all_day\'] ) ) {
        if ( empty($vars[\'_start_time\'] ) || empty( $vars[\'_end_time\'] ) ) {
            _e(\'Both Start time and End time need to be specified if the event is not an all-day event\');
            die();              
        }
        elseif ( strtotime( $vars[\'_start_date\']. \' \' .$vars[\'_start_time\'] ) > strtotime( $vars[\'_end_date\']. \' \' .$vars[\'_end_time\'] ) ) {
            _e(\'Start date/time cannot be after End date/time\');
            die();
        }
    }
}

//everything ok, allow submission
echo \'true\';
die();
}