How to call a database connection function in classes OOP? - php

Question

I want to be able to call a function which connects to my database, without creating multiple objects, including or having to write the same construct in each class. I Basically want to call a construct function in other classes.
like this below.
class Database{
public function __construct(){
$this->conn = new mysqli("host", "user", "password", "db");
// Check connection
if (!$this->conn) {
die("Connection failed: ".mysqli_connect_error());
}
}
}
class User{
// call Database->__construct();
}
class OtherClass{
// call Database->__construct();
}
ofcourse this isn't the way to go but i don't really know what would be a viable way.
I thought maybe this would work. but it doesn't
Making a new Database object in class to construct a connection
class Database{
public function __construct(){
$this->conn = new mysqli("host", "user", "password", "db");
// Check connection
if (!$this->conn) {
die("Connection failed: ".mysqli_connect_error());
}
}
}
class User{
$conn = new Database();
}
Dependecy injection or constructor injection seems like a nice solution. But i don't know if it's made for something like this and how to apply it.
class Database{
public function connection(){
$this->conn = new mysqli("host", "user", "password", "db");
// Check connection
if (!$this->conn) {
die("Connection failed: ".mysqli_connect_error());
}
}
}
class User{
private $db;
public function __construct(Database $conn){
$this->db = $conn;
}
}

Answer 1

Here what i am doing for connection
class DBConnection{
protected static $db;
private function __construct() {
try {
self::$db = new PDO( 'mysql:host=localhost;dbname=db_abc', 'root', '' );
//self::$db = new PDO( 'mysql:host=localhost;dbname=db_phonebook', 'root', 'QAZwsx2016!' );
self::$db->setAttribute( PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION );
}
catch (PDOException $e) {
echo "Connection Error: " . $e->getMessage();
}
}
public static function getInstance() {
if (!self::$db) {
new DBConnection();
}
return self::$db;
}
public function __destruct() {
$db=NULL;
}
}
And here how I am using to another model class
class User{
private $db;
public function __construct() {
$this->db = DBConnection::getInstance();
}
public function getUsers(){
//....................
//....................
//$sql =
$query = $this->db->prepare($sql, array(PDO::ATTR_CURSOR => PDO::CURSOR_SCROLL));
$query->execute();
$customers = $query->fetchAll();
//return .........
}
If you want pure OOP way, please look into the factory methods, and look facade design pattern, Its all about how you gonna achieve some this.
This one is my way (simple way) but to architecture better see the different design patterns.
One useful article here link
and
Design Patterns with PHP-The right way link