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Understanding OOP with PDO Connection
Object-oriented programming (OOP) offers a structured approach to software design, modeling real-world entities as objects. In the context of database connectivity using PHP's PDO (PDO), understanding the correct usage of OOP is crucial.
Consider a database connection scenario where you have multiple classes: a Database class handling the database connection and a User class performing operations on the database. Let's analyze the given code:
Database.php:
class Database { private $conn; private $dsn = 'mysql:dbname=test;host=127.0.0.1'; private $user = 'root'; private $password = ''; public function __construct() { $this->conn = new PDO($this->dsn, $this->user, $this->password); return $this->conn; } }
User.php:
include "database.php"; class User { private $conn; public function __construct() { $this->conn = new Database(); } public function login() { $stmt = $this->conn->prepare("SELECT username, usermail FROM user"); // Rest of the code... } }
App.php:
$user = new User(); $list = $user->login(); // Rest of the code...
Errors and Desired Behavior:
Executing this code results in an error indicating that prepare() is an undefined method for Database.
Proper Implementation:
To fix this, we need to follow these guidelines:
Updated Code:
database.php:
// Define database connection parameters $host = '127.0.0.1'; $db = 'test'; $user = 'root'; $pass = ''; $charset = 'utf8'; // Create a PDO connection $dsn = "mysql:host=$host;dbname=$db;charset=$charset"; $opt = [ \PDO::ATTR_ERRMODE => \PDO::ERRMODE_EXCEPTION, \PDO::ATTR_DEFAULT_FETCH_MODE => \PDO::FETCH_ASSOC, \PDO::ATTR_EMULATE_PREPARES => false, ]; $pdo = new \PDO($dsn, $user, $pass, $opt);
User.php:
class User { private $conn; public function __construct(\PDO $pdo) { $this->conn = $pdo; } public function getUsers() { return $this->conn->query("SELECT username, usermail FROM user")->fetchAll(); } }
App.php:
include 'database.php'; $user = new User($pdo); $list = $user->getUsers(); // Rest of the code...
This code will establish a database connection through database.php and pass the connection instance to the User class constructor. User can then execute queries using the PDO object stored in $conn.
Benefits:
This approach provides numerous benefits over the original implementation:
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