PHP PDO类编程:致命错误:在布尔值上调用成员函数fetchAll() [英] PHP PDO class programming:Fatal error: Call to a member function fetchAll() on boolean

问题描述

我是php类编程的新手，这是我的数据库类.

I am new to the class programming in php ,Here is my database class.

class Database
{
    private $_connection;
    private static $_instance; //The single instance
    private $_host = 'localhost';
    private $_username = 'root';
    private $_password = '';
    private $_database = 'admission_portal';

    //connect to database
    public function connectDb()
    {
        try {
            $this->_connection  = new \PDO("mysql:host=$this->_host;dbname=$this->_database", $this->_username, $this->_password);
            /*** echo a message saying we have connected ***/
            echo 'Connected to database';
        } catch (PDOException $e) {
            echo $e->getMessage();
        }
    }
    //run the query
    public function run($sql)
    {
        $result=$this->_connection->prepare($sql);
        return $result->execute();
    }
}

我将其扩展到核心类以执行一些数据库操作.

I am extending this to core class to do some database operations.

class Core extends Database 
{

    //get all the universities
    public function getData()
    {

        Database::connectDb();
        $sql = 'SELECT * FROM `adm_universities`';  
        $r=Database::run($sql);
        print_r($r->fetchAll(PDO::FETCH_OBJ));

    }
}

现在我正在以这种方式调用getData函数.

Now i am invoking getData function like this way.

 $db=new Core();
 $db->getData();

但是我会得到这个

致命错误:在布尔值上调用成员函数fetchAll(). 我的代码有什么错误?请帮助我

Fatal error: Call to a member function fetchAll() on boolean. What is the error in my code?please help me

推荐答案

只需要在run()方法中返回$result:

public function run($sql)
    {
        $result=$this->_connection->prepare($sql);
        $result->execute();
        return $result;
    }

返回$result->execute();将返回true，因为execute()成功.您需要返回$result的当前状态.

Returning the $result->execute(); is returning true because the execute() succeeded. You need to return the current state of $result.

看看是否可行.

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