How to use mysqli _construct with database connection

[Tuyet]

I am attempting to connect to the database (which was successfully). However, I can not extend the connection to execute other functions. In my example below,
the output is not giving me what I expected. There seem to be two connections and my escaped text which I called ($data = $query->select($text); ) does not execute.

OUTPUT:
Connection established! Now:Connection established! Now:
text passed =Brian O'Dell
text can be escaped =


INDEX.PHP (main page):

include("database_connect.php");
include("query_builder.class.php");

$text = "Brian O'Dell";

$query = new QueryBuilder;
$data = $query->select($text);

DATABASE_CONNEC T.PHP:

public $host = 'localhost';
public $db_username = 'root';
public $db_password = 'password';
public $db_name = 'customer';

protected $mysqli;

public function __construct() {}

public function connect()
{
$this->mysqli = new mysqli($this->host,$this->db_username,$this->db_password,$this->db_name);

if ($mysqli->connect_error) {
die('Connect Error (' . $mysqli->connect_errno . ') '. $mysqli->connect_error);
}		
else
{
echo "Connection established! Now:";
}

} 

public function db_close()
{
$this->mysqli->close();
} 

public function __destruct() {}

QUERY_BUILDER.C LASS.PHP:

class QueryBuilder
{

public function __construct()
{
	$this->connect = Db_Connect::connect();	
}

public function __destruct()
{
	Db_Connect::db_close();
}

public function select($sql=false)
{
	
	echo "<br>text passed =".$sql."<br>";
	$newtxt =  $this->mysqli->real_escape_string($sql);
	echo "text can be escaped = ".$newtxt;

}
}

[Dormilich]

as far as I can see, you don’t have a $this->mysqli instance. $this->connect is null (Db_Connect::con nect() doesn’t return anything) and I guess Db_Connect should be a Singleton (though it’s currently called incorrectly (in static context)).

… I’d probably find more issues if I see the whole code