在PHP中将属性从一种方法传递到另一种方法

Question

I'm trying out classes and PHP:PDO. I've set up a simple class to try out some stuff but I'm getting an error "Undefined variable: conn" error.

class Cms {

    function __construct() {
        try {
            $conn = new PDO('mysql:host=localhost;dbname=blog', 'root', '');
            $conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
        } catch(PDOException $error) {
            echo 'error: ' . $error->getMessage();
        }
    }

    public function read() {
        $query = $conn->query("SELECT * FROM posts");
    }
}

To my knowledge this is probably because the $conn PDO object is not being passed onto the read method because it's being set in the construct method. What is the best(proper) way to let the read method be able to use the $conn attribute?

Answer 1

class Cms {

    private $_conn;

    function __construct() {
        try {
            $this->_conn = new PDO('mysql:host=localhost;dbname=blog', 'root', '');
            $this->_conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
        } catch(PDOException $error) {
            echo 'error: ' . $error->getMessage();
        }
    }

    public function read() {
        $query = $this->_conn->query("SELECT * FROM posts");
    }
}

So you create a private property, assign your PDO instance to it and use

Some documentation: http://www.php.net/manual/en/language.oop5.properties.php