搜索功能无法显示任何内容

Question

我正在尝试搜索功能，我在名为Topic的文件中创建了一个公共函数，我尝试在index.php中调用该方法，但它没有显示任何内容，我认为问题在于while语句，但我并不完全确定。

Topic.php

class Topic{

public function searchPosts($postTags)
  {
    $conn = Db::getInstance();

   $statementSearch = $conn->prepare("SELECT * FROM topics INNER JOIN posttopic ON topics.topicID=posttopic.topicID INNER JOIN posts ON posttopic.postID=posts.postID WHERE naam = :naam");
   $statementSearch->bindValue(":naam", $postTags);
   return $statementSearch->execute(array());


  }
}  

的index.php

    spl_autoload_register(function ($class) {
    include_once("classes/" . $class . ".php");
    });  

$_SESSION['KEYWORD'] = array();
$postArray = array();

//$allResults2 = array();

if (isset($_POST['Find'])) {

if (!empty($_POST['Find'])) {

    $searchTopic = new Topic();
    $postTags = $_POST['naam'];
    $searchTopic->searchPosts($postTags);

    while ($row = $statementSearch->fetch(PDO::FETCH_ASSOC)) {
        $_SESSION['KEYWORD'][] = $row['postImageUrl'];
        $postArray[] = $row['postID'];
    }
}


if (count($_SESSION['KEYWORD']) === 0) {
    $error = "Sorry no results!";

}

}

这是应该打印的html。

        <?php
        foreach (array_combine($_SESSION['KEYWORD'], $postArray) as           $imageLink => $i) {
            echo "<a href='./pin.php?postid=$i' ><img src='" . $imageLink . "'</a>";

        }
        ?>