ho questi due errori e non riesco a risolverli :
Warning: Parameter 2 to mysqli_stmt::bind_param() expected to be a reference, value given in C:\Users\giuliano\PhpstormProjects\catalogoMvc\lib rerie\dbCon.php on line 86

Warning: mysqli_stmt::bind_param(): Number of elements in type definition string doesn't match number of bind variables in C:\Users\giuliano\PhpstormProjects\catalogoMvc\lib rerie\dbCon.php on line 99

lo script si compone di due classi
$query = "SELECT * FROM members WHERE email=? LIMIT 1";
$this->dbCon->preparestatement($query);
$param_type = 'S';
$this->dbCon->bindParamsToStatement($param_type,array($email));
$this->dbCon->execStartement();
$this->dbCon->storeResult();

$user_id = 0;
$username = '';
$db_password = '';
$salt = '';
$email='';

$this->dbCon->bindResult( array( &$user_id, &$username, &$db_password, &$salt,&$email));
$this->dbCon->fetchStartement();
$password = hash('sha512', $password . $salt);

// inizzio metodi statement
public function preparestatement($statement){

$this->_statement = $this->_dbCon->prepare($statement);
}
public function bindParamsToStatement( $type, $params ){
call_user_func_array( array( $this->_statement, 'bind_param' ), array_merge( (array) $type, $params ) );
}
public function execStartement(){

return $this->_statement->execute();
}

public function storeResult(){

$this->_statement->store_result();
}
public function bindResult($params){

call_user_func_array( array( $this->_statement, 'bind_param' ), $params );
}
public function fetchStartement(){

return $this->_statement->fetch();
}
public function numRows(){

$this->_statement->num_rows();
}

public function closestartement(){
$this->_dbCon->close();
grazie per l aiuto