PHP understanding OOP Concepts - php

Question

I'm just new to PHP and i cant understand why the code bellow doesn't works.
If i do the same code but not using class things works just fine.
<?php
class DAL
{
public $Conn;
public function __construct()
{
global $Conn;
$Conn = new PDO("mysql:host=localhost;dbname=football", "root","");
$Conn->setAttribute(PDO::ATTR_DEFAULT_FETCH_MODE, PDO::FETCH_OBJ);
}
}
class BLL
{
public function GetSeason()
{
$conn = new DAL();
$result = $conn->Conn->query("Select * from season");
print_r($result->fetchAll());
}
}
?>

Answer 1

If I understand right, DAL is Data access layer and BLL is Business logic layer.
Both usually represented not by one class or object, but rather contain objects that represent different levels of abstractions in your application.
Data access layer consists of Data access objects and Business logic layer consists of Business Objects. So you should have one Data access object for each Business Object. In general Data access objects should share one interface (i.e. should extend same Data access object abstract class):
abstract class DataAccessObject
{
protected $conn;
public function __construct($conn)
{
$this->conn = $conn;
}
abstract public function all();
abstract public function get($id);
abstract public function save($object);
abstract public function delete($object);
}
So with your example, the code can look like the following. Here is your season DAO:
final class SeasonDataAccessObject extends DataAccessObject
{
public function all()
{
$query = $this->conn->query('SELECT * FROM `season`');
$seasons = [];
foreach ($query->fetchAll() as $result) {
$seasons[] = $this->hydrate(new Season, $result);
}
return $seasons;
}
public function get($id)
{
// Execute select statement and hydrate result into
// Season Business Object.
// Should return instancs of Season.
}
public function save($season)
{
return null === $season->id
? $this->insert($season)
: $this->update($season);
}
public function delete($season)
{
// Execute delete statement.
}
private function hydrate(Season $season, $result)
{
// Fill $season attributes with values from $result.
}
private function update(Season $season)
{
// Execute update statement.
}
private function insert(Season $season) {
// Execute insert statement.
}
}
And here goes your season Business object:
abstract class BusinessObject
{
private $id;
public function setId($id)
{
$this->id = $id;
return $this;
}
public function getId()
{
return $this->id;
}
}
final class Season extends BusinessObject
{
// Some properties of Season and setters and getters for them.
}
And finally, you can use it all in your program:
$conn = new PDO('mysql:host=localhost;dbname=football', 'root', '');
$conn->setAttribute(PDO::ATTR_DEFAULT_FETCH_MODE, PDO::FETCH_OBJ);
$seasonDAO = new SeasonDataAccessObject($conn);
$seasons = $seasonDAO->all();
print_r($seasons);
I guess you got the lingo from "Microsoft Application Architecture Guide" or somewhere else in the Microsoft world (your attributes naming also speaks for it:)). In the modern world, I guess Data access object is Repository and the Business object is Entity.
This is pretty advanced stuff that concerns not even OOP, but Object-oriented design. So you must understand OOP first, because as it was mentioned in the comments, now your code is procedural. Wrapping code in class doesn't make code object-oriented (at the end of the day, this is Object-oriented programming, not Class-oriented programming;))
So, please start with some tutorial on the subject of OOP in PHP (i.e. this one), and gradually you will get better in this.

Answer 2

Done!!!!!
Thank you guys so much!!!
class DAL
{
public $Conn;
public function __construct()
{
$this->Conn = new PDO("mysql:host=localhost;dbname=football",
"root","");
$this->Conn->setAttribute(PDO::ATTR_DEFAULT_FETCH_MODE, PDO::FETCH_OBJ);
}
}
class BLL
{
public function GetSeason()
{
$conn = new DAL();
$result = $conn->Conn->query("Select * from season");
print_r($result->fetchAll());
}
}