anyone know how to use or statement in the query function that bucky create at php oop login and registration

i want to achieve : if this is not available then choose form here (kind of thing)

php code :

public function query($sql , $params = array()){
$this->_error = false;
if($this->_query = $this->_pdo->prepare($sql)){
$x = 1;
foreach($params as $param){
$this->_query->bindValue($x, $param);
$this->_result = $this->_query->fetchAll(PDO::FETCH_OBJ);
$this->_count = $this->_query->rowCount();
$this->_error = true;
return $this;