在布尔值上调用成员函数 fetch()-php问题

Call to a member function fetch() on boolean(在布尔值上调用成员函数 fetch())

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问题描述

我收到此错误:

致命错误:在布尔值上调用成员函数 fetch()C:xampphtdocs epogeneratormodeldatabase.php 第 34 行

Fatal error: Call to a member function fetch() on boolean in C:xampphtdocs epogeneratormodeldatabase.php on line 34

当我运行此代码时:

    class database
    {
        private $user = 'root';
        private $pass = '';
        public $pdo;

        public function connect() {
            try {
                $this->pdo = new PDO('mysql:host=localhost; dbname=generatordatabase', $this->user, $this->pass);
                echo 'Połączenie nawiązane!';
            }
            catch(PDOException $e) {
                echo 'Połączenie nie mogło zostać utworzone: ' . $e->getMessage();
            }
        }

        public function createTable() {

                        $q = $this->pdo -> query('SELECT * FROM article');
                          while($row = $q->fetch()) {
                              echo $row['id'].' ';
                          }
                          $q->closeCursor();
        }
    }

    ?>

推荐答案

根据 PHP 手册 PDO::查询

PDO::query() 返回一个 PDOStatement 对象，或者失败时返回 FALSE.

PDO::query() returns a PDOStatement object, or FALSE on failure.

看起来您的查询失败(在第 33 行)并因此返回 BOOLEAN (false)，可能是因为在执行时，PDO 尚未连接到包含名为 article.在 connect() 方法中，我看到它尝试连接到名为generatordatabase"的数据库；确保在调用 createTable() 之前建立此连接，否则确保它包含一个名为article"的表.

It looks like your query is failing (on line 33) and thus returning a BOOLEAN (false), likely because at that point in execution, PDO has not connected to a database that contains a table called article. In the connect() method I see that it tries to connect to a db called 'generatordatabase'; ensure this connection is being made prior to calling createTable(), otherwise ensure that it contains a table called 'article'.

我建议添加更多代码示例，例如在触发错误之前调用此类/方法的代码.

I would recommend adding some more code examples, for instance the code that calls this class/method before the error is triggered.

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