短代码中的PHP代码

基本上，我有一行代码：

<?php echo do_shortcode('[O_U user_name="operator" 
blocked_message="This page is restricted for guests."] 
**Content Goes here** [/O_U]'); ?>

---

只需关闭PHP标记，然后//对html进行一些回显，然后像这样打开

<?php
    $database_name = "rams";
    $mydb = new wpdb(DB_USER, DB_PASSWORD, $database_name, DB_HOST);
    $mydb -> show_errors();

    //Populate languages
    $languages = $mydb -> get_results(
        'SELECT * FROM language_skills'
    );

    foreach ($languages as $language){ ?>
       <!--Write your html hear--> 
       <option><?=$language?></option>
    <?}
?>


我正在尝试，但在显示错误行中“$mydb->”之后，浏览器中的所有内容都会变成html文本。我从show_errors（）开始看到，一直到结尾。试着删除那行它不是关于这行，而是关于“->”
<?php
    $database_name = "rams";
    $mydb = new wpdb(DB_USER, DB_PASSWORD, $database_name, DB_HOST);
    $mydb -> show_errors();

    //Populate languages
    $languages = $mydb -> get_results(
        'SELECT * FROM language_skills'
    );

    foreach ($languages as $language){ ?>
       <!--Write your html hear--> 
       <option><?=$language?></option>
    <?}
?>