Question

I want to pass a mysqli object to a class. I create the object in one file:

$host = 'host';
$user = 'username';
$pw = 'pw';
$db = 'db';

$link = new mysqli($host,$user,$pw,$db);

which is included in one page:

include 'php/mysql.php';
include 'php/classes/Class.Dataconnector.php';
$dc = new Dataconnector($link);

and the class looks like this:

class Dataconnector {
    protected $_link;
    protected $_stub;

    function __construct(mysqli $link) {
        $_link = $link;
    }

    public function getPageContent($stub) {
        $query = "select * from contents where pageId = (select id from pages where stub = '$stub')";
        $result = mysqli_query($_link,$query);
        return $result;
    }
}

But I get this error:

Warning: mysqli_query() expects parameter 1 to be mysqli, null given in \php\classes\Class.Dataconnector.php on line 18

What is wrong ?

Answer 1

You need to use $this when accessing the class property $_link in your class.

In your constructor, you have:

$_link = $link;

This should be:

$this->_link = $link;

In your getPageContent() method you have:

$result = mysqli_query($_link,$query);

This should be:

$result = mysqli_query($this->_link,$query);