更新语句mySQL问题

当用户更新他们发表的博客文章时，我在更新数据库的posts表时遇到问题。

事件流-用户写一篇博客文章，将其保存到数据库中，然后他们可以返回并编辑它。编辑会显示一个预先填充的html表单，表单中填充了posts表中的数据。然后，用户可以更改标题和内容，当他们按下更新时，表单中的发布值应替换posts DB中原始帖子的标题和内容——所有其他列保持不变。

目前我的数据库似乎没有更新，不知道为什么。使用html/php/sql/pdos的组合来执行sql语句-这对我的新手来说非常复杂，任何帮助都将不胜感激。代码（UPDATE语句位于底部，也是最有问题的）：

// begin edit post
    if(isset($_GET['editPost'])) {
            $editPostId = $_GET['editPost'];
            $sqlEditPostCheck = <<<EOD
            SELECT author, id FROM posts WHERE author = '$currentUserId'
EOD;
            $stmtEditPostCheck = $pdo->prepare($sqlEditPostCheck);
            $stmtEditPostCheck->execute();
            $ableToEdit = false;
            while ($row = $stmtEditPostCheck->fetch(PDO::FETCH_ASSOC)) {
                if($editPostId === $row['id'] && $currentUserId === $row['author']) { $ableToEdit = true; }
            }
            if($ableToEdit === true) {
                $editPost_Title = "";
                $editPost_Content = "";
                $sqlEditPostPreFills = <<<EOD
            SELECT id, post_title, content FROM posts WHERE id="$editPostId"
EOD;
                $stmtEditPost = $pdo->prepare($sqlEditPostPreFills);
                $stmtEditPost->execute();   
                while ($row = $stmtEditPost->fetch(PDO::FETCH_ASSOC)) {
                    $editPost_Title = $row['post_title'];
                    $editPost_Content = $row['content'];
                    $editPostId = $row['id'];
                }    
                $content = <<<EOD
                <form action="?profile&editPost="$editPostId" method="post">
            <h1>Edit Post</h1>
            <div class="form-group">
              <input name="Epost_title" type="text" id="Epost_title" value="$editPost_Title" class="form-control">
            </div>
                        <div class="form-group">
              <textarea class="form-control" name="Epost_content" id="Epost_content" value="" rows="6">$editPost_Content</textarea>
            </div>
            <div style="text-align: right;">
              <button type="submit" name="update" style="width: 30%;" class="btn btn-success btn-lg">Update</button>
            </div>
                </form>
            <hr />
EOD;
        } // end IF ableToEdit
        $updatedContent = "";
            if(isset($_POST['Epost_content'])) { $updatedContent = $_POST['Epost_content']; }
    $updatedTitle = "";
            if(isset($_POST['Epost_title'])) { $updatedTitle = $_POST['Epost_title']; }
    if(isset($_POST['Epost_content']) && isset($_POST['Epost_title'])) {
    $sqlUpdatePost = <<<EOD
    UPDATE posts SET post_title='$updatedTitle', content='$updatedContent' WHERE posts.id='$editPostId' AND posts.author='$currentUserId';
EOD;
            $stmtUpdate = $pdo->prepare($sqlUpdatePost);
            $stmtUpdate->execute();
                }
    }
    // end edit post