我正在为一位朋友的WordPress网站上创建一个相当简单的自定义页面，但我在正确保存元数据库的内容时遇到了一些实际困难。WordPress的行为似乎不像我所期望的PHP那样，因此，当我将echo语句放在某个地方以查看它的位置时，它们并不总是出现，即使代码必须运行时也是如此。非常奇怪。

有人能指出我做错了什么吗？（很抱歉代码太多！）

function metabox_exhibition_setup() {
    /* Add \'start_date\' hook. */
    add_meta_box(\'gc_start_date\', 
            esc_html__(\'Exhibition Start Date\'),
            \'create_metabox_exhibition_start_date\',
            \'gc_exhibition\', 
            \'side\', 
            \'default\');

    /* Add \'finish_date\' hook. */
    add_meta_box(\'gc_finish_date\', 
            esc_html__(\'Exhibition Finish Date\'),
            \'create_metabox_exhibition_finish_date\',
            \'gc_exhibition\', 
            \'side\', 
            \'default\');

    /* Add \'subtitle\' hook. */
    add_meta_box(\'gc_subtitle\', 
            esc_html__(\'Exhibition Subtitle\'),
            \'create_metabox_exhibition_subtitle\',
            \'gc_exhibition\', 
            \'normal\', 
            \'core\');

    add_action( \'save_post\', \'save_metabox_exhibition\', 10, 2 );        
}

/* Save the meta box\'s post metadata. */
function save_metabox_exhibition( $post_id, $post ) {
    $fields = 0;

    if($_POST) {
    $metaboxes[0][\'nonce\'] = $_POST[\'exhibition_finish_date_nonce\'];
    $metaboxes[0][\'data\'] = $_POST[\'gc_finish_date\'];
    $metaboxes[1][\'nonce\'] = $_POST[\'exhibition_start_date_nonce\'];
    $metaboxes[1][\'data\'] = $_POST[\'gc_start_date\'];
    $metaboxes[2][\'nonce\'] = $_POST[\'exhibition_subtitle_nonce\'];
    $metaboxes[2][\'data\'] = $_POST[\'gc_subtitle\'];
    $fields = count($metaboxes);
        $fields = count($metaboxes);
    }

    //print_r($metaboxes);

    for($i = 0; $i <= $fields ; $i++ ) {
        /* Verify the nonce before proceeding. */
        if ( !isset( $metaboxes[$i][\'nonce\'] ) || !wp_verify_nonce( $metaboxes[$i][\'nonce\'], basename( __FILE__ ) ) )
                return $post_id;

        /* Get the post type object. */
        $post_type = get_post_type_object( $post->post_type );

        /* Check if the current user has permission to edit the post. */
        if ( !current_user_can( $post_type->cap->edit_post, $post_id ) )
                return $post_id;

        /* Get the posted data and sanitize it */
        $new_meta_value = ( isset( $metaboxes[$i][\'data\'] ) ? sanitize_html_class( $metaboxes[$i][\'data\'] ) : \'\' );

        /* Get the meta key. */
        $meta_key = $metaboxes[$i][\'data\'];

        /* Get the meta value of the custom field key. */
        $meta_value = get_post_meta( $post_id, $meta_key, true );

        /* If a new meta value was added and there was no previous value, add it. */
        if ( $new_meta_value && \'\' == $meta_value )
                add_post_meta( $post_id, $meta_key, $new_meta_value, true );

        /* If the new meta value does not match the old value, update it. */
        elseif ( $new_meta_value && $new_meta_value != $meta_value )
                update_post_meta( $post_id, $meta_key, $new_meta_value );

        /* If there is no new meta value but an old value exists, delete it. */
        elseif ( \'\' == $new_meta_value && $meta_value )
                delete_post_meta( $post_id, $meta_key, $meta_value );
    }