我想在我的drupal网站上使用securimage captcha，
我有一份注册表格，我在同一页面上提交该表格。
Securimage配置文档说（here）在表单处理器的第一行使用session_start（）。
我在同一页面上同时拥有表单和表单处理器，那么我应该在哪里编写session_start（）？
这是我的代码
<form id="user_form" action="" method="post">
<div class="form">
<?php if (isset($errors) && count($errors)>0) : ?>
<ul class="error-list">
<?php foreach ($errors as $e) : ?>
<li><?php echo $e; ?></li>
<?php endforeach; ?>
</ul>
<?php endif; ?>
<div class="form-section">
<div class="col">
<div class="row">
<label class="two-rows">Select your<br />account type <span>*</span></label>
<select name="uf_user_type" style="width:173px;" class="required">
<option value="">None Selected</option>
<option value="<?php print JOB_SEEKER_ROLE; ?>">Job Seeker</option>
<option value="<?php print MASTER_EMPLOYER_ROLE; ?>">Employer</option>
</select>
<div class="cl"> </div>
<em class="status"></em>
</div>
<div class="row">
<label>First Name <span>*</span></label>
<input type="text" class="field required" name="uf_first_name" />
<div class="cl"> </div>
<em class="status"></em>
</div>
<div class="row">
<label>Last Name <span>*</span></label>
<input type="text" class="field required" name="uf_last_name" />
<div class="cl"> </div>
<em class="status"></em>
</div>
<div class="row">
<label>Email <span>*</span></label>
<input type="text" class="field required email-field" name="uf_mail" />
<div class="cl"> </div>
<em class="status"></em>
</div>
<div class="row">
<div class="cl"> </div>
</div>
<div class="row">
<label class="two-rows">Image <span>*</span></label>
<img id="captcha" src="/sites/all/themes/jobnow/site/securimage/securimage_show.php" alt="CAPTCHA Image" height="45" width="160" style="border:1px solid #b9b9b9"/>
<a href="#" onclick="document.getElementById('captcha').src = '/sites/all/themes/jobnow/site/securimage/securimage_show.php?' + Math.random(); return false">
<img src="/sites/all/themes/jobnow/site/securimage/images/refresh.png" height="30" width="30" alt="Reload Image" onclick="this.blur()" align="bottom" border="0">
</a>
</div>
</div>
<div class="col right-col">
<div class="row">
<label class="two-rows">How did you <br />hear about us? <span>*</span></label>
<select name="uf_hear_about_us" style="width:173px;" class="required">
<option value="">None Selected</option>
<option>Colleague/Friend</option>
<option>Search Engine</option>
<option>LinkedIn</option>
<option>Twitter</option>
<option>Facebook</option>
<option>Advertisement</option>
<option>In The News</option>
<option>Trade Show/Organization</option>
<option>Other</option>
</select>
<div class="cl"> </div>
<em class="status"></em>
</div>
<div class="row">
<p class="hint"><?php echo bfstring('hint_register_password'); ?></p>
<label>Password <span>*</span></label>
<input type="password" class="field required" id="pass1" name="uf_password" />
<div class="cl"> </div>
<em class="status"></em>
</div>
<div class="row">
<label class="two-rows">Confirm <br />Password <span>*</span></label>
<input type="password" class="field required" id="pass2" name="uf_password2" />
<div class="cl"> </div>
<em class="status"></em>
</div>
<div class="row">
<label class="labelBlack">
<input type="checkbox" class="check required" name="uf_terms" value="1" <?php if(isset($_POST['uf_terms']) && $_POST['uf_terms'] == 1) print 'checked'; ?> />
</label>
<p>I accept the <a href="<?php echo url('legal'); ?>"target="_blank">Terms of Service.</a></p>
<div class="cl"> </div>
</div>
<div class="row">
<div class="cl"> </div>
</div>
<div class="row">
<label class="two-rows">What code is<br />in the image?<span>*</span></label>
<input type="text" class="field required" name="captcha_code" size="10" maxlength="6" />
<div class="cl"> </div>
<em class="status"></em>
</div>
</div>
<div class="cl"> </div>
</div>
<div>
</div>
<div class="form-actions">
<span class="required-info"><strong>*</strong> required</span>
<input type="submit" class="form-submit" value="Create Account" />
<a href="javascript:history.go(-1);">Cancel</a>
<div class="cl"> </div>
</div>
</div>
</form>
if ($_SERVER['REQUEST_METHOD'] == 'POST')
{
$securimage = new Securimage();
$isSecurImageValid=$securimage->check($_POST['captcha_code']) != false;
if ($validator->validateRules($_POST) && $isSecurImageValid)
{
$new_user = new stdClass();
$new_user->roles = array();
$username_base =strtolower(preg_replace('~(.*)\@.*~', '$1', site_rgpc($_POST['uf_mail'])));
$usernames = array();
}
else
{
$errors = $validator->getErrors();
if(!$isSecurImageValid)
$errors[]="The Security Code wasn't entered correctly.";
}
当我在我的网站上集成此代码时，它表示您的验证码对于每次尝试都是错误的。
我没有得到什么问题？
相同的代码在我的另一个类似网站上没有session_start（）的情况下工作。
请帮帮我