我为我的自定义主题创建了这个元框。我以为我遵守了所有的指导原则，但我遇到了麻烦。meta框和所有字段都会显示出来，但当我更新时，数据不会保存。

Meta box addition:

function drw_events_metabox(){
    add_meta_box(\'events_info\', \'EVENT INFO\', \'drw_evenet_info_clbk\', \'drw-events\', \'side\', \'high\');
}

function drw_evenet_info_clbk($post){
    wp_nonce_field(\'drw_event_info\', \'drw_event_info_nonce\');
    $datevalue = get_post_meta( $post->ID, \'_event_date_valkey\', true);
    $starttimevalue = get_post_meta( $post->ID, \'_event_time_valkey\', true);
    $endtimevalue = get_post_meta( $post->ID, \'_event_endtime_valkey\', true);
    $covervalue = get_post_meta( $post->ID, \'_event_cover_valkey\', true);
    $freeEvent = get_post_meta( $post->ID, \'_event_free_valkey\', true);
    $stdTicketLink = get_post_meta( $post->ID, \'_event_stdticket_valkey\', true);
    $customTicketLink = get_post_meta( $post->ID, \'_event_customTicketLink_valkey\', true);
    $eventCancelled = get_post_meta( $post->ID, \'_event_cancel_valkey\', true);


    //event date
    echo\'<br><label for="drw_event_date_field">Event Date </label>\';
    echo \'<input type="date" id="drw_event_date_field" name="drw_event_date_field" value="\'.esc_attr($datevalue).\'" required/><br><br><hr><br>\';

    //event time
    echo\'<label for="drw_event_time_field">Event start time </label>\';
    echo \'<input type="time" id="drw_event_time_field" name="drw_event_time_field" value="\'.esc_attr($starttimevalue).\'" required/><br><br>\';


    echo\'<label for="drw_event_endtime_field">Event end time </label>\';
    echo \'<input type="time" id="drw_event_endtime_field" name="drw_event_endtime_field" value="\'.esc_attr($endtimevalue).\'" required/><br><br><hr><br>\';

    //event price
    echo\'<label for="drw_event_free_field">Event is free </label>\';
    echo\'<input type="checkbox" id="drw_event_free_field" name="drw_event_free_field" value="\'.esc_attr($freeEvent).\'" checked/><br><br>\';

    echo\'<label for="drw_event_cover_field">Event cover $ </label>\';
    echo \'<input type="number" id="drw_event_cover_field" name="drw_event_cover_field" value="\'.esc_attr($covervalue).\'" size="2"/><br><br><hr><br>\';


    //event ticket
    echo \'<h2><strong><em>Choose a ticket purchase link</em></strong></h2><br>\';
    echo\'<label for="drw_event_stdtktlink_field">Default link </label>\';
    echo \'<input type="checkbox" id="drw_event_stdtktlink_field" name="drw_stdtktlink_field" value="#" checked/><br><br>\';
    echo\'<label for="drw_event_customTicketLink_field">Custom link </label>\';
    echo \'<input type="text" id="drw_event_customTicketLink_field" name="drw_customTicketLink_field" value="\'.esc_attr($customTicketLink).\'"/><br><br><hr><br>\';

    //event cancellation
    echo \'<h2><strong><em>**Use only for event cancellation!</em></strong></h2><br>\';
    echo\'<label for="drw_event_cancelled_field">Event Cancelled </label>\';
    echo \'<input type="checkbox" id="drw_event_cancelled_field" name="drw_event_cancelled_field" value="\'.esc_attr($eventCancelled).\'"/><br><br><hr><br>\';

}

add_action(\'add_meta_boxes\', \'drw_events_metabox\');

Saving meta box data:

function save_drw_events_metabox_data( $post_id ) {

    if( ! isset( $_POST[\'drw_event_info_nonce\'] ) ){
        return;
    }

    if( ! wp_verify_nonce( $_POST[\'drw_event_info_nonce\'], \'save_drw_events_metabox_data\') ) {
        return;
    }

    if( defined(\'DOING_AUTOSAVE\') && DOING_AUTOSAVE ){
        return;
    }

    if( ! current_user_can( \'edit_post\', $post_id ) ) {
        return;
    }


    $event_date = sanitize_text_field( $_POST[\'drw_event_date_field\'] );
    $event_time = sanitize_text_field( $_POST[\'drw_event_time_field\'] );
    $event_entime = sanitize_text_field( $_POST[\'drw_event_endtime_field\'] );
    $event_free = sanitize_text_field( $_POST[\'drw_event_free_field\'] );
    $event_cover = sanitize_text_field( $_POST[\'drw_event_cover_field\'] );
    $event_linkdef = sanitize_text_field( $_POST[\'drw_stdtktlink_field\'] );
    $event_tix = sanitize_text_field( $_POST[\'drw_customTicketLink_field\'] );
    $event_cancel = sanitize_text_field( $_POST[\'drw_event_cancelled_field\'] );


    if( ! isset( $_POST[\'drw_event_date_field\'] ) ) {
        return;  
        update_post_meta($post_id, \'_event_date_valkey\', $event_date);
    }

    if( ! isset( $_POST[\'drw_event_time_field\'] ) ) {
        return;
        update_post_meta($post_id, \'_event_time_valkey\', $event_time);
    }

    if( ! isset( $_POST[\'drw_event_endtime_field\'] ) ) {
        return;
        update_post_meta($post_id, \'_event_endtime_valkey\', $event_entime);
    }

    if( ! isset( $_POST[\'drw_event_cover_field\'] ) ) {
        return;
        update_post_meta($post_id, \'_event_cover_valkey\', $event_cover);
    }


    if( ! isset( $_POST[\'drw_event_free_field\'] ) ) {
        return;   
        update_post_meta($post_id, \'_event_free_valkey\', true);
    } else {
        update_post_meta( $post_id, \'_event_free_valkey\', FALSE );
    }


    if( ! isset( $_POST[\'drw_stdtktlink_field\'] ) ) {
        return;
        update_post_meta($post_id, \'_event_stdticket_valkey\', $event_linkdef);
    }

    if( ! isset( $_POST[\'drw_customTicketLink_field\'] ) ) {
        return;
        update_post_meta($post_id, \'_event_customTicketLink_valkey\', $event_tix);
    }


    if( ! isset( $_POST[\'drw_event_cancelled_field\'] ) ) {
        return;
        update_post_meta($post_id, \'_event_cancel_valkey\', true);
    } else {
        update_post_meta( $post_id, \'_event_cancel_valkey\', FALSE );
    }

}

add_action( \'save_post\', \'save_drw_events_metabox_data\');

请帮忙。