gistfile1.txt

public function __construct(){

    $servername = "localhost";
    $username = "root";
    $password = "";
    $dbname = "dbname";
    $this->dbh = new PDO("mysql:host=$servername;dbname=$dbname", $username, $password);
    $this->dbh->setAttribute(PDO::ATTR_EMULATE_PREPARES, false);
    $this->dbh->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
}
	
	
public function one(){
	  $sth = $this->dbh->prepare('select * from ...');
}

public function __construct(\PDO $pdo) {
$this->db = $pdo;
}