我已经创建了一个元框，它有一个选择下拉列表，我想在用户从元框中选择特定选项时在帖子中显示它。我想不出是怎么回事。这是我的元框代码。

<?php
function display_post_options(){
    global $post;
    wp_nonce_field( basename( __FILE__ ), \'post_options_nonce\' ); 
    $post_options_select_value =  get_post_meta($post->ID,\'post_options_select\',true);

?>



    <label for="options-select">Choose Your Post Layout:</label>
    <select name=\'post_options_select\' id="options-select">
        <option id=\'right-sidebar\' value=\'right\' name=\'right_sidebar\' <?php selected($post_options_select_value, \'right\'); ?> >Right sidebar</option>
        <option id=\'left-sidebar\' value="left" name=\'left_sidebar\' <?php selected($post_options_select_value, \'left\'); ?>>Left Sidebar</option>
        <option id=\'no-sidebar\' value="no" name=\'no_sidebar\' <?php selected($post_options_select_value, \'no\'); ?>>No Sidebar</option>
    </select>


<?php
}

function post_options(){
    add_meta_box( 
        \'post-options\',
        \'Post Options\',
        \'display_post_options\',
        \'post\',
        \'advanced\',
        \'high\',
        $callback_args
    );
}

function save_post_options($post_id){

    if (if_user_can_save($post_id, \'post_options_nonce\')) {
        update_post_meta($post_id, \'post_options_select\', $_POST[\'post_options_select\']);
    }

}

function if_user_can_save($post_id, $nonce){

    //Check if post is autosave
    $is_autosave = wp_is_post_autosave($post_id);
    //Check if it is a Revision
    $is_revision = wp_is_post_revision($post_id);
    //Is the nonce valid
    $is_valid_nonce = ( isset( $_POST[ $nonce ] ) && wp_verify_nonce( $_POST[ $nonce ], basename( __FILE__ ) ) );
    return !($is_autosave || $is_revision) && $is_valid_nonce;

}

function display_content( $content ){
    $test = get_post_meta(get_the_ID(), \'options-select\', true);
    $content .= $test;
    print_r($test);
    return $content;
}

add_action(\'add_meta_boxes\', \'post_options\');
add_action( \'save_post\', \'save_post_options\', 10, 2 );
add_action(\'the_content\', \'display_content\');
?>