我正在尝试向自定义帖子类型中添加一个元框，并在前端显示文本。

我制作了一个元框，如下所示：

array(
    \'name\'   => __( \'<b>Schema</b>\', \'themeum-soccer\'),
    \'id\'     => \'schema_group\',
    \'type\'   => \'group\',
    \'fields\' => array(
        array(
            \'name\' => __(\'schema\', \'themeum-soccer\'),
            \'id\'   => \'schema_knvb\',
            \'desc\' => __(\'Paste hier de php snippit\', \'themeum-soccer\' ),
            \'type\' => \'textarea\',
            \'std\'  => \'\',
        ),
        array(
            \'name\' => __( \'Naam Trainer\', \'themeum-soccer\' ),
            \'id\'   => "test123",
            \'desc\' => __( \'Naam Trainer(ex: Arno Kuppen)\', \'themeum-soccer\' ),
            \'type\' => \'text\',
            \'std\'  => \'\',
        ),
    )

现在，它保存在我正在使用的插件中，但当我将以下代码放入我的自定义帖子模板中时：

<div role="tabpanel" class= "tab-pane fade" id="schema">
    <div>
        <?php echo rwmb_meta( $schema_knvb ); ?>
    </div>   
</div>

为什么它只打印“Array”（见下图）？

$schema_group = rwmb_meta( \'schema_group\' );
$schema_knvb = isset( $schema_group[\'schema_knvb\'] ) ? $schema_group[\'schema_knvb\'] : \'\';
echo $schema_knvb;