检索数据库表信息OOP [重复]

I am trying to retrieve my database rows using OOP I keep getting an error though. I feel like I am missing something simple to make this work. My code is below:

Class CommentFactory {      
    public function getImage(PDO $conn){
        $stmt2 = $conn->prepare('SELECT * FROM `pictures`');
        $stmt2->execute();

        return $stmt2;
    }
}


$statement = new CommentFactory();
$statement->getImage($conn);
while ($idOfComment = $statement->fetch(PDO::FETCH_ASSOC)) {
    echo $idOfComment['photo_id'];          
}

The error I am getting is:

Fatal error: Call to undefined method CommentFactory::fetch() in /var/www/CommentSystem/includes/Classes.php on line 29

I just recently began trying to program in OOP so my understanding is still vague.

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You are only returning a value from the method getImage(), therefore you should do:

Class CommentFactory {

    protected $conn;

    public function getImage($conn){
        $stmt2 = $conn->prepare('SELECT * FROM `pictures`');
        $stmt2->execute();

        return $stmt2;
    }
}


$statement = new CommentFactory();
$values = $statement->getImage($conn);
while ($idOfComment = $values->fetch(PDO::FETCH_ASSOC)){
    echo $idOfComment['photo_id'];

}

Edit: However, as engvrdr noted, this is not the best you can do. You could the method to return the array, furthermore, you can pass the connection in the constructor as shown here:

Class CommentFactory {

    protected $conn;

    public function __construct($conn) {
      $this->con = $conn;
      }

    public function getImage(){
        $stmt2 = $this->conn->prepare('SELECT * FROM `pictures`');
        $stmt2->execute();
        return $values->fetchAll(PDO::FETCH_ASSOC);
    }
}


$statement = new CommentFactory($conn);
foreach ($statement->getImage() as $Image){
    echo $Image['photo_id'];    
}

$statement variable is a instance of a CommentFactory class so it doesn't have a fetch method, that's why you are getting error.

you can either assign STMT object to a variable and loop through that variable like

$stmt = $statement->getImage();
while($id = $stmt->fetch(PDO::FETCH_ASSOC))

But i don't advise you to do it.

First of all, injecting db connection to a object method doesn't feel right to me, you can inject the connection object while you are creating CommentFactory object like;

class CommentFactory{
    private $conn;
    public $images;

    public function __construct($connection){
        $this->conn = $connection;
    }

    public function getImage(){
        $stmt2 = $this->conn->prepare('SELECT * FROM `pictures`');
        $stmt2->execute();
        while ($idOfComment = $stmt2->fetch(PDO::FETCH_ASSOC)){
            $this->images[] = $idOfComment['photo_id'];

        }
    }

}

$statement = new CommentFactory($conn);
$statement->getImage();
foreach($statement->images as $photo_id)
    echo $photo_id;
}

by the way, if you mean Factory design pattern by naming like CommentFactory,i advise you to have a look at example at wikipedia (http://en.wikipedia.org/wiki/Factory_method_pattern#PHP)