我無(wú)法弄清楚我的 PHP 有什么問(wèn)題，但 INSERT 似乎總是失敗。當(dāng)我提交表單時(shí)，什么也沒(méi)有發(fā)生，也沒(méi)有任何錯(cuò)誤消息發(fā)送到我的數(shù)據(jù)庫(kù)<form action="" method="POST">  <div class="form-group mt-4">    <label for="exampleInputEmail1">Title</label>    <input type="text" class="form-control" name="title" aria-describedby="emailHelp" required>  </div>  <div class="form-group">    <label for="exampleInputPassword1">Products to buy</label>    <textarea class="form-control" name="products" rows="3" required></textarea>  </div>  <div class="form-group">    <label for="exampleInputPassword1">Comments</label>    <input type="text" class="form-control" name="comments" aria-describedby="emailHelp" required>  </div>  <button type="submit" class="btn btn-info">Submit</button></form><?php $title = null;if (isset($_POST['title'])) {    $title = htmlspecialchars($_POST['title']);}$products = null;if (isset($_POST['products'])) {  $products = htmlspecialchars($_POST['products']);}$comments = null;if (isset($_POST['comments'])) {  $comments = htmlspecialchars($_POST['comments']);}$pdo = new PDO('mysql:host=localhost;dbname=liste_course;charset=utf8', 'root', '', [  PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,  PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC]);$sql = "INSERT INTO content(id, title_content, products_content, comments_content) VALUES('','$title','$products','$comments')";?>