连接注入故障排除

As has been suggested, I am trying to use the connection injection technique to allow my main class to operate. The injection code is from a class on another file. See fig A from connection.php

class qcon{

public static $conn;

function dbcon()
{


     if (empty($conn)) 
     {
         $host = 'x';
         $username = 'x';
         $password = 'x';
         $dbname = 'x';
         $conn = mysqli_connect($host , $username  , $password ,$dbname) or die("Oops! Please check SQL connection settings");
     }

     return $conn;
}

}

Here, I have my class injection code that is a method within my main class. See class.php on fig B

    class dbcats {
    var $conn;
    public function __construct(qcon $dbcon)
    {
        $this->conn = $dbcon;
    }

function getResult(){

            $result = mysqli_query($this->conn , "SELECT * from member" ); // Error see end of question
            if ($result) {
                return $result;
            } 
            else {
                die("SQL Retrieve Error: " . mysqli_error($this->conn));
            }
        }
}

And finally, see fig C for the call I make within the webpage.

$db1 = new qcon();
$db1->dbcon();
$helper = new dbevent($db1);
$result = $helper->getResult();

The above is causing the following

Warning: mysqli_query() expects parameter 1 to be mysqli, object given in C:\xxxxxxxxxxxxxx\webpage.php on line 35

Would someone kindly be able to look at what I have done and point out specifically what I'm doing wrong, and how to correct the scripts to get them to operate.

You don't take care of the returned $conn.

$db1 = new qcon();
$db1->dbcon();//This line returns the connection
$helper = new dbevent($db1);
$result = $helper->getResult();

It should be like this.

$db1 = new qcon();
$conn = $db1->dbcon();
$helper = new dbevent($conn);
$result = $helper->getResult();

You have a lot of problems in your code, here is the revised code( please find the difference yourself)

 class Qcon
 {

    public static $conn;

    public static function connection()
    {

        if (empty(self::$conn)) {
            $host = 'x';
            $username = 'x';
            $password = 'x';
            $dbname = 'x';
            self::$conn = mysqli_connect($host, $username, $password, $dbname) or die("Oops! Please check SQL connection settings");
        }

        return self::$conn;
    }
}

And then:

$helper = new dbevent(Qcon::connection());
$result = $helper->getResult();