<form id="commentform" action="wp-comments-post.php" method="post">
 <p>
    <input id="author" tabindex="1" size="30" name="author">
    <label>Name <span class="required">
    (required)    </span> </label>
  </p>
  <p>
    <input id="email" tabindex="2" size="30" name="email">
    <label>Email <span class="required">
    (required)    </span></label>
  </p>
  <p>
    <input id="url" tabindex="3" size="30" name="url">
    <label>Website</label>
  </p>
 
<p>
    <textarea id="comment" name="comment" rows="10" cols="100"></textarea>
</p>
<p>
    <input type="image" src="submit.png&quot/">
    <input type="hidden" value="524" name="comment_post_ID">
    <input id="_wp_unfiltered_html_comment" type="hidden" value="0d870b294b" name="_wp_unfiltered_html_comment">
</p>
</form>

<?php
$postfields = array();
$postfields["action"] = "submit";
$postfields["author"] = "Spammer";
$postfields["email"] = "spammer@spam.com";
$postfields["url"] = "http://www.iamaspammer.com/";
$postfields["comment"] = "I am a stupid spammer.";
$postfields["comment_post_ID"] = "123";
$postfields["_wp_unfiltered_html_comment"] = "0d870b294b";
//Url of the form submission
$url = "http://www.ablogthatdoesntexist.com/blog/suggerer_site.php?action=meta_pass&id_cat=0";
$useragent = "Mozilla/5.0";
$referer = $url; 
 
//Initialize CURL session
$ch = curl_init($url);
//CURL options
curl_setopt($ch, CURLOPT_POST, 1);
//We post $postfields data
curl_setopt($ch, CURLOPT_POSTFIELDS, $postfields);
//We define an useragent (Mozilla/5.0)
curl_setopt($ch, CURLOPT_USERAGENT, $useragent);
//We define a refferer ($url)
curl_setopt($ch, CURLOPT_REFERER, $referer);
//We get the result page in a string
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
//We exits CURL
$result = curl_exec($ch);
curl_close($ch);
 
//Finally, we display the result
echo $result;
?>