How to access variables in OOP - php

Question

I am trying to find a way to get the variable called $connect to run but don't know how.
Filename: /engine/init.php
class Engine {
function MySQL() {
$connect = new PDO("mysql:host=$db_host;dbname=$db_name;charset=$db_char", $db_user, $db_pass);
}
}
Filename: /inc/database.php
require 'engine/init.php;
$engine = new Engine;
$conn = $engine->MySQL;
// Activate $connect variable
If it's not clear, please request for more info.
Thanks,
CrAzYz_

Answer 1

You will have to update the class to access members outside.
You have several options to do it.
1: store the connection in a public property
class Engine {
public $connection;
public function MySQL() {
$this->connection = new PDO("mysql:host=$db_host;dbname=$db_name;charset=$db_char",$db_user, $db_pass);
}
}
This way you can retrieve it by
$engine = new Engine();
$engine->MySQL();
$conn = $engine->connection;
2: Make the function return the connection
class Engine {
public function MySQL() {
return new PDO("mysql:host=$db_host;dbname=$db_name;charset=$db_char",$db_user, $db_pass);
}
}
This way your example will work (if you use Mysql as a function):
$engine = new Engine();
$conn = $engine->MySQL();
3: A more complicated but generally better aproach:
class Engine {
protected $connection;
public function __construct($db_host, $db_name, $db_user, $db_pass $db_char = "utf-8") {
$this->connection = new PDO("mysql:host=$db_host;dbname=$db_name;charset=$db_char",$db_user, $db_pass);
}
public function MySQL() {
if ( !$this->connection instanceof PDO ) {
throw new Exception("Connection is not set up");
}
return $this->connection;
}
}
This would work almost as you wanted, except you cant access the connection directly (its protected), but only through the MySql function. This way if you forgot to init the connection an exception is thrown.
$engine = new Engine("localhost", "db_name", "user", "pass");
$conn = $engine->MySQL(); // you don't even need to save the connection to a local variable, because the function only references the connection and won't start a new one
Footnote:
If you had to as this kind of question you should probably look up and learn more about OOP. For php this is a start: http://php.net/manual/en/language.oop5.php

Answer 2

About to run off so this is a little quickly done.
class Engine
{
public $db;
public function connect($host, $database, $charset, $user, $pass)
{
$this->db = new PDO("mysql:host=$host;dbname=$database;charset=$charset", $user, $pass);
}
}
First of we have your Engine class that you want to create, we've created a property named db on the class that we can access with ->db. We also have a method called connect which we pass our database variables into so that PDO can connect to our database.
Now we pass in our database credentials to our connect method, in a production environment I really would advise against hard coding these and instead use something like environment variables.
$engine = new Engine();
$engine->connect('127.0.0.1', 'example_database', 'UTF-8', 'root', 'root');
We can then use our newly initiated PDO connection like so:
$statement = $engine->db->query('SELECT * FROM some_table');
$result = $statement->execute();
That should at least give you a starting point, there are other ways to go about this but I didn't want to stray too far from your original code.
Also if anyone spots anything wrong, let me know and i'll update it when I'm back in, need to run off in a sec.