Question

我收到一个错误，说准备功能是空的，我之前已经有了这个并且可以解决它没有问题，但我不明白我现在做错了什么。致命错误显示：

致命错误：未捕获错误：调用成员函数prepare（） null在C：\ xampp \ htdocs \ OOP \ Artist-System \ classes \ Db.php：43 Stack trace：＃0 C：\ xampp \ htdocs \ OOP \ Artist-System \ classes \ Artist.php（94）： Db->查询（＆＃39; SELECT name，pl ...＆＃39;，Array）＃1 C：\ xampp \ htdocs \ OOP \ Artist-System \ index.php（11）：Artist-＆gt; select（）＃2 {main}抛出C：\ xampp \ htdocs \ OOP \ Artist-System \ classes \ Db.php on 第43行

Db类：

class Db
{
    private $servername;
    private $username;
    private $password;
    private $dbname;
    private $charset;

public function __construct($servername, $username, $password, $dbname, $charset)
{
    $this->servername = $servername;
    $this->username = $username;
    $this->password = $password;
    $this->dbname = $dbname;
    $this->charset = $charset;
}

private function connect()
{
    try {
        $dsn = "mysql:host=".$this->servername.";dbname=".$this->dbname.";charset=".$this->charset;
        $options = [
            PDO::ATTR_ERRMODE            => PDO::ERRMODE_EXCEPTION,
            PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC,
            PDO::ATTR_EMULATE_PREPARES   => false,
        ];
        $pdo = new PDO($dsn, $this->username, $this->password, $options);
        return $pdo;
    } catch (PDOException $e) {
        $e->getMessage();
    }
}

public function query($query, $data)
{
    $stmt = $this->connect()->prepare($query);
    $stmt->execute($data);
    $queryWords = explode(' ', trim($query));
    if ($queryWords[0] == "SELECT") {
        return $stmt->fetchAll();
    }
}

艺术家类，错误位于第93-94行：

public function select()
{
    $select = "SELECT name, playcount, listeners, image FROM artist";
    return $this->db->query($select, array());
}

未捕获错误：即使初始化数据库对象，也要在null上调用成员函数prepare（）

0 个答案: