Php OOP select query

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PHP

OOP

I'm trying to learn OOP and i'm trying to create a class which will select me info from a table and a line that i choose. (trying my best to explain it good, not sure if i'm doing very well tho)

This is my code in the class:

class SelectQuery {
   
    public function db_select($query_table, $query_extra) {
       
        //$result = mysqli_query($conn, "SELECT * FROM `ideas` WHERE `Accepted` = 1 ORDER BY RAND() LIMIT 1");
        //$query = 'SELECT * FROM '.$query_table.' '.$query_extra.'';
        //$results = $this->con->query($query);
       
        $this->con = mysqli_connect('localhost', 'root', '', 'forum');
       
        $results = $this->con->prepare('SELECT * FROM '.$query_table.' '.$query_extra.'');
        $results->execute();
       
        return $results;
    }
}

And this is the code in the actual page:

include_once 'Classes/SelectQuery.php';
 
$SelectQuery = new SelectQuery();
 
$query_table = 'category';
$query_extra = '';
 
$SelectQuery->db_select($query_table, $query_extra);
 
$date = $db_select->$result;
 
$date = mysqli_fetch_assoc($result);
 
echo $date;
 
while($categories = $result->fetch_assoc())
{
    echo '<p>';
    echo $categories['ID'].' ';
    echo $categories['Name'].'</p>';
   
    while($forums = $result_forum->fetch_assoc())
    {
        echo $categories['Name'].'</p>';
    }
}

The problem isnt in the class(i think), it's in the actual page when i'm trying to get the info that i want, there is no error until here:

$SelectQuery->db_select($query_table, $query_extra);

but after that line when i'm trying to really get the info there is a lots of errors and i'm probably doing it wrong... i would like to know how can i fix it, thanks :)

What I have tried:

I tried a lots of things like i said, i'm pretty new at this and i have no idea why it's not working...