html - Error when trying to insert a comment on a blog post php -

i trying insert comments on blog post , keep getting error message. don't know if database set correctly, or if i'm missing syntax error. have form page , handle page. form:

<h1><center> add comment form</center></h1> <form action="hc.php" method="post"> <fieldset>  <h3>post comment.</h3> <br> <textarea name="comment"cols="50"rows="10"id="comment" >  </textarea><br> <input type="hidden" name="comid" value="'.$comid .'"/> <input type="hidden" name="blogid" value="'.$blogid .'"/>  <input type="submit"value="submit"name="submit" /> <input type="reset"value="clear"> </fieldset> </form> 

my handle page following:

  <?php include ('./includes/mysqli_connect.php');  $blogid = $_session['blogid'];  $comment = $_session['comment']; $comdate = $_session['comdate']; $comid = $_session['comid']; $userid = $_session['userid'];  //if (isset($_get['blogid']) && isset($_get['userid']) && isset($_get['comment'])){ $query = "insert comments(comid, blogid, userid, comment, comdate) values ('$comid', '$blogid','$userid','$comment','$comdate')"; $result= @mysqli_query($dbc,$query);  $comid=null; $blogid=null; $userid=null;  if ($results) { echo "thank  information has been submitted."; } else {     echo "there error! " . mysqli_error($dbc); } ?> 

i new @ php , appreciate help.

the error message is:

there error! cannot add or update child row: foreign key constraint fails (codecrew_users.comments, constraint comments_ibfk_1 foreign key (blogid) references blog (blogid))

$query = "insert comments(comid, blogid, userid, comment, comdate) values ('$comid', '$blogid','$userid','$comment','$comdate')"; 

so... table comments has field on requires foreign key.

i'm not sure value causing error 1 of values not match id in table.

so 1 of these has invalid value:

'$comid', '$blogid','$userid','$comment','$comdate'