表用户名和密码的验证建议

Question

请看一下这段代码。这是个人可以编辑其详细信息的限制区域。目前我不希望个人编辑用户名和密码。是否有任何实现来保护（验证）这些字段，但细节仍应显示在文本框中。

public function blabla($lllll)
{
    try {
        $con = new PDO( DB_DSN, DB_USERNAME, DB_PASSWORD );
        $con->setAttribute( PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION );
        $book = "SELECT * FROM x WHERE id =".$usr;
        $stmt = $con->prepare($book);
        $stmt->execute();
        $get = $stmt->fetch(PDO::FETCH_ASSOC);
        $ts = new Account;
        echo("<div id='box'>
        <div class='box-header'>". $get['']."</div>
        <div class='box-content'>
        <form method='post'>
        <table width='50%'>
        <tr>
            <td>Name:</td>
            <td><input type='text' size='0' name='name' value='".$get['name']."'  /></td>
        </tr>
        <tr>
            <td>Surname:</td>
            <td><input type='text' size='0' name='surname' value='".$get['surname']."'  /></td>
        </tr>
        <tr>
            <td>Username:</td>
            <td><input type='text' size='0' name='username' value='".$get['username']."'  /></td>
        </tr>
        <tr>
            <td>Password:</td>
            <td><input type='text' size='0' name='password' value='".$get['password']."'  /></td>
        </tr>
        <tr>
            <td>E-mail:</td>
            <td><input type='text' size='0' name='email' value='".$get['email']."'  /></td>
        </tr>
        ");
        echo("</table></form></div></div>");
    }catch( PDOException $e ) {
        return $e->getMessage();
    }
}