Php PDO extend class using it in other classes without extending class

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PHP and PDO class question

I was wondering if anyone could help I have a basic php PDO extend class and i wanted to use a global $db in other class to do all the mysql stuff. I can connect to database and that but just want to use a global variable which i can access in any class.

But I dont want to extend the database class with my new classes, i also don't want to pass the database connection var in the class constructor.

is there a way to do this?

here's some coding sample what i want to achive excuse any coding errors..

//--DATABASE CLASS
class Database Extends PDO {

    protected $database_hostname = DB_HOST;
    protected $database_username = DB_USER;
    protected $database_password = DB_PASSWORD;
    protected $database_name = DB_NAME;
    protected $database_type = DB_TYPE;

    public function __construct() {

        try {
            parent::__construct($this->database_type . ':host=' . $this->database_hostname . ';dbname=' . $this->database_name, $this->database_username, $this->database_password, array(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION));
        } catch (PDOException $e) {
            echo 'ERROR: ' . $e->getMessage();
        }
    }

}



//--TEST CLASS
class test1 {

    //--INSIDE MY FUNCTIONS I WANT TO BE ABLE TO USE A $db to do my msql stuff
    public function test1a() {

        $stmt = $db::prepare('SELECT * FROM table');
        $stmt->excute();
    }

}

//--TEST CLASS 2
class test2 {

    public function test2a() {

        $stmt = $db::prepare('SELECT * FROM table');
        $stmt->excute();
    }

}

//--CREATE THE DATABASE GLOBAL
 $db = new Database();
 $testers = new test2();

If i did the above i would get an error saying that $db is Undefined variable: db

Thank you for help but parent would not work as im not extending the class — rwebdev, Feb 03 '13 at 16:42

score 1 · Answer 1 · answered Feb 03 '13 at 16:15

1

Although I read that was not recommended, you can do the following: outside of all the classes (in the global scope) initialize your connection:
$db = new Database();
Then in every function where you need your Db connection, write this:
global $db;

answered Feb 03 '13 at 16:15

Andre Polykanine

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Here is one of many threads on the topic of why globals are generally considered bad practice: http://stackoverflow.com/questions/357187/when-are-global-variables-acceptable – leftclickben Feb 03 '13 at 16:16
There is nothing wrong with using `global` keyword on global variables. `$db` is surely one of them. – Your Common Sense Feb 03 '13 at 16:22
Thanks for help, what about making a static var able every where? – rwebdev Feb 03 '13 at 16:41
What do you actually mean? If you have to call static methods (`$db::doSomething()`), then no difference. Make a `global $db;` and that'll be it) – Andre Polykanine Feb 05 '13 at 00:20
Oh ok cause i have a static class so i could do that ... thanks – rwebdev Feb 08 '13 at 14:19

score 1 · Answer 2 · answered Feb 03 '13 at 16:16

1

When using $db inside a function, PHP expects the variable to be in the local function scope. To access the global variable, use either

$GLOBALS['db']->prepare (important: Use -> instead of ::; calling prepare statically will not work), or
global $db; $db->prepare(...);

answered Feb 03 '13 at 16:16

helmbert

35,797
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Thank you for help but could a make it a static class and return it as static var... not sure how i could do this.. – rwebdev Feb 03 '13 at 16:44

Php PDO extend class using it in other classes without extending class

2 Answers2