PHP Ajax Captcha(Securimage) issue

Question

Hi, i have a little problem with captcha validation using php and ajax. this is the php validation:

if(trim($code) == '') {
$error_captcha = '<p class="error">some empty error....</p>';
$errorc = 'error';
$error = $erdiv;
 } else if (trim($code) != ''){
require_once ('securimage.php');
$captcha = new Securimage();
$valid = $captcha->check($code);
if ($valid == false) {
echo '<p class="error">some captcha incorrect error...</p>';
$error_captcha .= '<p class="error"></p>';
   }
  }

this is my form:

<form class="wufoo leftLabel page" action="javascript:send_action('register.php',3)">

<div class="info">
 <h2>פזור - טופס רישום</h2>
 <?php echo $error; ?>
</div>

<ul>    

<li class="right <?php echo $erroru; ?>">
 <div class="col">
  <input type="text" class="field text large" id="user_register" value="<?php echo $username; ?>" maxlength="255" />
  <?php echo $error_user; ?>
   </div>
    <label class="desc">
  <span class="req">*</span>
    <?php small('שם משתמש'); ?>
   </label>
  <p class="instruct"><small>שם המשתמש</small></p>
 </li>

<li class="right <?php echo $errorp; ?>">
 <div class="col">
  <input type="password" class="field text large" id="pass_register" value="<?php echo $pass; ?>" maxlength="255" />
  <?php echo $error_pass; ?>
   </div>
    <label class="desc">
        <span class="req">*</span>
  <?php small('סיסמא'); ?>
   </label>
  <p class="instruct"><small>נא הזן את סיסמתך</small></p>
 </li>


<li class="right <?php echo $errorp.''.$errorpv; ?>">
 <div class="col">
  <input type="password" class="field text large" id="pass_val_register" value="<?php echo $pass_val; ?>" maxlength="255" />
  <?php echo $error_pass_val.''.$error_pass; ?>
   </div>
      <label class="desc">
  <span class="req">*</span>
    <?php small('אימות סיסמא'); ?>
   </label> 
  <p class="instruct"><small>נא הזן את סיסמתך שנית</small></p>
 </li>

  <li class="right <?php echo $errore; ?>">
 <div class="col">
  <input type="text" class="field text large" id="email_register" value="<?php echo $email; ?>" maxlength="255" />
    <?php echo $error_email; ?>
 </div>
  <label class="desc">
  <span class="req">*</span>
  <?php small('כתובת דוא"ל'); ?>
   </label>
  <p class="instruct"><small>נא הקפד להזין כתובת דוא"ל חוקית על מנת שתוכל להפעיל את חשבונך</small></p>
 </li>
    <li class="right captcha"></li>
   <li class="right <?php echo $errorc; ?>">
 <div class="col">
  <input type="text" class="field text large" id="captcha_register" maxlength="255" />
    <p><img src="securimage_show.php?sid=<?php echo md5(uniqid(time())); ?>"></p> 
    <?php echo $error_captcha; ?> 
 </div>
  <label class="desc">
  <span class="req">*</span>
  <?php small('קוד אבטחה'); ?>
   </label>
  <p class="instruct"><small>נא הזן את קוד האבטחה כפי שמופיע בתמונה</small></p>
 </li>
 <li class="buttons ">
      <input id="saveForm" name="saveForm" class="btTxt submit" type="submit" value="שלח" />


   </li>
</ul>
</form>

(that's thbrew there) The problem is that the variable $eror_captcha isn't set at all when entering a wrong string.