fatal error is causing no results to appear (Mysql

I am getting this error in my script which I think is causing the search bar not to work:

Fatal error: Call to a member function bind_param() on a non-object in /web/stud/xxx/Mobile_app/previousquestions.php on line 89.

The line it is pointing to is this line:

$stmt->bind_param("s",$each);

What needs to be done in order to fix this error? At the moment the error is causing no results to appear after the user has submitted the content within the search bar.

  <?php

        //connect to db

          $questioncontent = (isset($_POST['questioncontent'])) ? $_POST['questioncontent'] : '';

        ?>

        <?php 

        if (isset($_GET['searchQuestion'])) {

        $searchquestion = $questioncontent;
        $terms = explode(" ", $searchquestion);
$parameters = array();

        $questionquery = "
        SELECT q.QuestionId, q.QuestionContent, o.OptionType, q.NoofAnswers, GROUP_CONCAT(an.Answer ORDER BY an.Answer SEPARATOR ' ') AS Answer, r.ReplyType, 
               q.QuestionMarks 
          FROM Answer an 
          INNER JOIN Question q ON q.AnswerId = an.AnswerId
          JOIN Reply r ON q.ReplyId = r.ReplyId 
          JOIN Option_Table o ON q.OptionId = o.OptionId 

                         WHERE ";

        $i=0;
        foreach ($terms as $each) {     
            $i++;         

            if ($i == 1){         
                $questionquery .= "q.QuestionContent LIKE ?";     
                } else {         
                    $questionquery .= "OR q.QuestionContent LIKE ?";    
                     } 
                     }  

                     $questionquery .= "GROUP BY q.QuestionId, q.SessionId ORDER BY "; $i = 0; foreach ($terms as $each) {     
                         $i++;      

            if ($i != 1)         
            $questionquery .= "+";     
            $questionquery .= "IF(q.QuestionContent LIKE ?,1,0)"; 
            } 

            $questionquery .= " DESC "; 

            $stmt=$mysqli->prepare($questionquery);      
    $parameters[] = ($each)   
    $stmt->execute($parameters);  
            $stmt->bind_result($dbQuestionId,$dbQuestionContent,$dbOptionType,$dbNoofAnswers,$dbAnswer,$dbReplyType,$dbQuestionMarks); 
            $questionnum = $stmt->num_rows();

        }

    ?>

It means that the $stmt variable isn't being set properly - I think you need spaces after the LIKE ? lines, as you're concatening GROUP BY right after it.

You need to check that the SQL statement you're generating is correct, and that the database connection is also working.