Use of included class in another class - php

Question

I'm trying to use a database class (ADOdb for PHP) but I don't know how to use it in another class.
Example:
<?php
include_once("adodb.inc.php");
$conn = NewADOConnection('mysql');
class Contacts {
public function getData(){
$conn->Connect(...);
//do something
}
}
?>
I think the problem is that I can not call $conn because its defined outside the class.
Notice: Undefined variable: conn
Fatal error: Call to a member function Connect() on a non-object
Maybe I'm doing it the wrong way, but I really don't know how to fix this.
Can somebody please help me out? Thanks a lot!

Answer 1

Why not simply do like this ?!
<?php
include_once("adodb.inc.php");
$conn = NewADOConnection('mysql');
$conn->Connect(...);
class Contacts {
protected $_connection;
public function __construct($conn)
{
$this->_connection = $conn;
}
public function getData(){
//do something
}
}
$contacts = new Contacts($conn);
$foobar = new FooBar($conn);
?>
It makes sense to establish connection outside the class, and then pass in already workable object. And of-course to share the same connection object among all the classes which require it.
P.S i would really reallly recommend to drop ADODB and start learning PDO.

Answer 2

You have a number of choices:
Use the global reserve word:
<?php
include_once("adodb.inc.php");
$conn = NewADOConnection('mysql');
class Contacts {
public function getData(){
global $conn;
$conn->Connect(...);
//do something
}
}
?>
Or pass $conn to your object on creation
$contacts = new Contacts($conn);
class Contacts {
protected $conn;
public function __construct($conn){
$this->conn = $conn;
}
public function getData(){
$this->conn->Connect(...);
//do something
}
}
?>
Or you could yous a Singleton data connection object. But that is considered a anti-pattern so I would inject your dependency as in option 2.

Answer 3

you need to reference the global variable:
<?php
include_once("adodb.inc.php");
$conn = NewADOConnection('mysql');
class Contacts {
public function getData(){
global $conn;
$conn->Connect(...);
//do something
}
}
?>
That said, you would probably be better off using dependency injection like this:
<?php
class Contacts {
private $db;
public function setDB($conn) {
$this->db = $conn;
}
public function getData(){
if (!$this->db) {
throw new Exception();
}
$conn = $this->db;
$conn->Connect(...);
//do something
}
}
?>
And then include your adodb include and instantiation in an initialization section.
Edit: Please see this article on Dependency Injection as getting into the habit of using this (and not globals) may save a lot of headaches down the road.

Answer 4

$conn is out of your variable scope. Use the following to make it work:
class Contacts {
public function getData(){
global $conn;
$conn->Connect(...);
//do something
}
}
Another way to do it is to have a reference to the variable inside your object:
class Contacts {
private $ref;
public function __construct($conn)
{
$this->ref = $conn;
}
public function getData(){
$ref->Connect(...);
//do something
}
}
$contacts = new Contacts($conn);