Php 致命错误：通过从数据库读取记录来调用布尔值上的成员函数fetch（）

我有readOne函数。此函数将从类别表中仅读取一条记录，并为名称和描述变量赋值。看起来是这样的：

public function readOne($id) {
    $stmt = $this->conn->prepare('SELECT name, description FROM categories WHERE id = '.$id)->execute();
    $result = $stmt->fetch(PDO::FETCH_ASSOC);
    $this->name = $result['name'];
    $this->description = $result['description'];
}

我试着用这个来称呼它：

<?php
if($_SERVER['REQUEST_METHOD'] == 'POST'){
if ( isset( $_POST['read'], $_POST['id']) ) {

    $cat = new Category($conn);

    $id = filter_input ( INPUT_POST , 'id', FILTER_SANITIZE_NUMBER_INT );


    echo $cat->readOne($id);
}}
?>
<div>
<h3>readOne():</h3>
<form action="" method="post">
<label>Category id :</label>
<input type="text" name="id" id="id" required="required" placeholder="Please Enter Id"/><br /><br />
<input type="submit" value="read" name="read"/><br />
</div>

编辑：连接代码：

<?php

class Database {

public function getConnection() {
    $result = false;
    try {
        $result = new PDO('mysql:host=localhost;dbname=demo', 'root', '');
    } catch(PDOException $e) { }
    return $result;
}
}
$db = new Database();
$conn = $db->getConnection();
if (!$conn) {
die("Error connecting to the database");
}

?>

---

您正在为

$stmt

分配返回值

execute（）

。您需要替换行

$stmt=$this->conn->prepare（'SELECT name，description FROM categories WHERE id='。$id）->execute（）带有：

$stmt = $this->conn->prepare('SELECT name, description FROM categories WHERE id = '.$id);
$stmt->execute();

查询执行代码需要进行如下更改：-

$stmt = $this->conn->prepare('SELECT name, description FROM categories WHERE id = "'.$id.'"'); 
$stmt->execute(); 
$result = $stmt->fetch(PDO::FETCH_ASSOC); 
$this->name = $result['name'];

将此代码用于您的问题您在接受答案后当前所问的内容（
但现在当我单击“阅读”按钮时，什么都没有发生？
）：-

<?php
session_start();
if($_SERVER['REQUEST_METHOD'] == 'POST'){
if ( isset( $_POST['read'], $_POST['id']) ) {

    $cat = new Category($conn);

    $id = filter_input ( INPUT_POST , 'id', FILTER_SANITIZE_NUMBER_INT );


    $_SESSION['description'] =  $cat->readOne($id);
}}
?>
<div>
<h3>readOne():</h3>
<form action="" method="post">
<label>Category id :</label>
<input type="text" name="id" id="id" required="required" placeholder="Please Enter Id"/><br /><br />
<input type="submit" value="read" name="read"/><br />
</div>
<div class= "description"><?php if(isset($_SESSION['description']) && !empty($_SESSION['description'])){ echo $_SESSION['description'];}?></div>


readOne（）：
类别id：





@Anant可以使用带有多个参数的
isset（）
。另外，
execute（）
返回一个布尔值，因此您不能执行您的建议。@MrCode您是对的。谢谢
<?php
session_start();
if($_SERVER['REQUEST_METHOD'] == 'POST'){
if ( isset( $_POST['read'], $_POST['id']) ) {

    $cat = new Category($conn);

    $id = filter_input ( INPUT_POST , 'id', FILTER_SANITIZE_NUMBER_INT );


    $_SESSION['description'] =  $cat->readOne($id);
}}
?>
<div>
<h3>readOne():</h3>
<form action="" method="post">
<label>Category id :</label>
<input type="text" name="id" id="id" required="required" placeholder="Please Enter Id"/><br /><br />
<input type="submit" value="read" name="read"/><br />
</div>
<div class= "description"><?php if(isset($_SESSION['description']) && !empty($_SESSION['description'])){ echo $_SESSION['description'];}?></div>