使用PDO對象進行Select查詢

Question

我是PDO的初學者。 我正在按照教程學習PDO。 我想使用一個簡單的select語句來獲取用戶ID。

但是當我運行index.php它不顯示任何echo ！ 我哪里錯了？

我有四個文件：

config =>設置用戶名和密碼...

DB_Connect：

class DB_Connect {

    // constructor
    function __construct() {

    }

    // destructor
    function __destruct() {
        // $this->close();
    }

    // Connecting to database
    public function connect() {
        require_once 'include/config.php';
        try {
            $hostname = DB_HOST ;
            $dbname   = DB_DATABASE;
            $dbh = new PDO("mysql:host=$hostname;dbname=$dbname", DB_USER, DB_PASSWORD);
        }
        catch(PDOException $e)
        {
            echo $e->getMessage();
        }

        return $dbh;
    }



}

---

DB_Functions：

class DB_Functions {

    private $db;

    //put your code here
    // constructor
    function __construct() {
        require_once 'DB_Connect.php';
        // connecting to database
        $this->db = new DB_Connect();
        $this->db->connect();
    }

    // destructor
    function __destruct() {

    }


    function getUsers(){

        $sql = "SELECT * FROM users";
        foreach ($this->$db->query($sql) as $row)
        {
            echo $row->id;
        }

        /*** close the database connection ***/
      //  $db = null;

    }
}

---

的index.php

<?php

    require_once 'include/DB_Functions.php';
    $qr = new DB_Functions();
    $qr->getUsers();



?>

Answer 1

db_connect

class DB_Connect {
    public $dbh;
    // constructor
    function __construct() {

    }

    // destructor
    function __destruct() {
        // $this->close();
    }

    // Connecting to database
    public function connect() {
        require_once 'include/config.php';
        try {
            $hostname = DB_HOST ;
            $dbname   = DB_DATABASE;
            $this->dbh = new PDO("mysql:host=$hostname;dbname=$dbname", DB_USER, DB_PASSWORD);
        }
        catch(PDOException $e)
        {
            echo $e->getMessage();
        }
    }
}

db_functions

class DB_Functions {

    private $db;

    //put your code here
    // constructor
    function __construct() {
        require_once 'DB_Connect.php';
        // connecting to database
        $this->db = new DB_Connect();
        $this->db->connect();
    }

    // destructor
    function __destruct() {

    }


    function getUsers(){

        $sql = "SELECT * FROM users";
        foreach ($this->db->dbh->query($sql) as $row)
        {
            echo $row->id;
        }

        /*** close the database connection ***/
      //  $db = null;

    }
}

您沒有數據庫連接，因為您現在正在將PDO連接分配給變量。 因此，其余腳本無法訪問您的連接。 至少，這就是我目前的想法。