Fatal error: Call to a member function query() PHP CLASS

Question

I\'m trying to write this class to connect and query my database, but I got this error:

Fatal error: Call to a member function query() on null in C:

Answer 1

You have to use $this to access properties of the own class.

$this->connection = ....

$result = $this->connection->...

It would be better if you used a constructor to initiate the connection, currently you are opening a new connection to the database every time you use the query method.

edit: Your class could look like this

connection = mysqli_connect($this->db_host, $this->db_user, $this->db_pass, $this->db_name) 
                or die("Error " . mysqli_error($this->connection));
    }

    public function db_query($query) {
        var_dump($query);
        $result = $this->connection->query($query);
        while ($row = mysqli_fetch_array($result)) {
            echo $row["COD_PRE"] . "
";
        }
    }

}

$con = new Db();
$con->db_query('SELECT `COD_PRE`, `CODE` FROM `test` WHERE `CODE` = 457 AND CONFIN = 1');
?>

I see no need for the properties to be static, so I changed them too.

The db_query method is in my opinion too unflexible, as it directly outputs your result. I would use fetch_all to return the whole resultset as an array. That way you can freely choose how you want to handle your results.