mysql_fetch_object with specific class

I developed an object-oriented guestbook and I have my Class GuestBookEntry:

class GuestBookEntry {
protected $id;
protected $entryDate;
protected $authorName;
protected $authorMail;  
protected $entryText; 

// getters, setters and specific functions are omitted
}

I also have a mysql table with the same names as columns.

Well, when I fetch guestbook entries, it seems to work, but it only displays the ID and the Date, which where returned by getters. The other things won't return to the template.

The code looks like this:

public function showEntries() { 
    $query = mysql_query('SELECT * FROM dng_entries ORDER BY id DESC');     
    while($entry = @mysql_fetch_object($query, 'GuestBookEntry')) {
        if(empty($entry)) {
        echo '<font color="white">Keine Eintr&auml;ge vorhanden...</font>';
        } else {    
        var_dump($entry);
        echo '<table class="table table-bordered entryfield" align="right">
                <thead>
                    <tr>
                        <td rowspan="2">'.$entry->getId().'</td>
                        <td width="20%">Datum:</td>
                        <td>Name:</td>
                        <td>Email:</td>
                    </tr>
                    <tr>
                        <td>'.$entry->getEntryDate().'</td>
                        <td>'.$entry->getAuthorName().'</td>
                        <td><a href="mailto:'.$entry->getAuthorMail().'">'.$entry->getAuthorMail().'</a></td>
                </thead>
                <tbody>
                    <tr>
                    <td width="10%" valign="middle">Eintrag:</td>
                    <th colspan="3" valign="top" height="100px">'.$entry->getEntryText().'</td>
                    </tr>
                </tbody>
            </table>';
        }
    }
}

Here's a var_dump of e.g. object:

object(GuestBookEntry)#2 (5) { ["id":protected]=> string(1) "2" ["entryDate":protected]=> int(1344696811) ["authorName":protected]=> NULL ["authorMail":protected]=> NULL ["entryText":protected]=> NULL }

update: well here is the rest of GuestBookEntry class:

public function __construct($authorName, $authorMail, $entryText) {
       $this->authorName    = $authorName;
       $this->authorMail    = $authorMail;
       $this->entryDate     = time();
       $this->entryText     = $entryText;
    }

    public function getId() {
       return $this->id;
    }
    public function getAuthorName() {
       return (String) $this->authorName;
    }
    public function getAuthorMail() {
       return (String) $this->authorMail;
    }
    public function getEntryDate() {
       return date('d.n.Y', $this->entryDate);
    }
    public function getEntryText() {
       return $this->entryText;
    }

    public function setAuthorName($authorName) {
       $this->authorName=$authorName;
    }   
    public function setAuthorMail($authorMail) {
       $this->authorMail=$authorMail;
    }
    public function setEntryDate($entryDate) {
       $this->entryDate=$entryDate;
    }
    public function setEntryText($entryText) {
       $this->entryText=$entryText;
    }