Why am I getting NULL when I try to initiate a connection?

Question

I have a class with global $connection but when I try to access it I am getting NULL. As you can see if i try to access within the constructor I do not get NULL. But from getConnection() I am getting NULL.

class DatabaseManipulation
{
    private $connection;

    function __construct()
    {
        global $connection;
        $connection = new mysqli("localhost", "root", "", "db");
        $result = $connection->query("select * from user");

        print_r($result); //I get an array
    }

    function getConnection(){
        global $connection;
        var_dump($connection); // I get -> object(DatabaseManipulation)#1 (1) { ["connection":"DatabaseManipulation":private]=> NULL } NULL 
    }

}

Same thing happens when I instantiate an object $connection = new DatabaseManipulation();. Am I doing something wrong? I want this to be done in OO way. Can anyone help me ?

score 1 · Accepted Answer · answered Dec 19 '16 at 10:49

1

You are using OO PHP not procedural. So change it to:

$this->connection = new mysqli("localhost", "root", "", "db");;

answered Dec 19 '16 at 10:49

Praveen Kumar Purushothaman

164,888
24
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score 1 · Answer 2 · edited May 23 '17 at 12:09

1

I want this to be done in OO way.

Then stop using global. You don't want to refer to a global state when you're in a class. A quick look to The Basics and you will find that a pseudo-variable $this is available inside your object.

class DatabaseManipulation
{
    private $connection;

    function __construct()
    {
        $this->connection = new mysqli("localhost", "root", "", "db");
    }

    function getConnection(){
        var_dump($this->connection);
    }
}

More about it:

edited May 23 '17 at 12:09

Community

1
1

answered Dec 19 '16 at 10:51

Federkun

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90

I am still getting error : Notice: Undefined variable: connection in.... – Naveen Niraula Dec 19 '16 at 11:00
where's your code? you should refer to `connection` using `$this`: `$this->connection->query("select * from user");` – Federkun Dec 19 '16 at 11:05
Did you read the code above? Also, read http://stackoverflow.com/questions/1523479/what-does-the-variable-this-mean-in-php – Federkun Dec 19 '16 at 11:08
Then change your code accordingly. Be aware that `$this->$connection` !== `$this->connection` – Federkun Dec 19 '16 at 11:12

Why am I getting NULL when I try to initiate a connection?

2 Answers2