将可变数量的参数传递给PDO语句并返回JSON obj

Question

This function takes an array of integers

  $this->grades

this array varies in size depending on what the user inputs. I can get it to work perfectly with only one number, but when I try more than one I run into the problem. Do I need to somehow concatenate the responses together before encoding them? Or is there a more efficient way to run this?

 private function retrieve_standards_one(){
    $dbh = $this->connect();
    for($x = 0; $x < (count($this->grades)); $x++){
    $stmt = $dbh->prepare("SELECT code, standard_one_id 
                           FROM standard_one 
                           WHERE grade_id = :grade_id 
                           ORDER BY standard_one_id");
    $stmt->bindParam(':grade_id', $this->grades[$x], PDO::PARAM_STR);
    $stmt->execute();
    $stnd = $stmt->fetchAll(PDO::FETCH_ASSOC);
    }
    $json = json_encode($stnd);
    return $json;
}

Answer 1

Just use an array to store the results and encode the array

 private function retrieve_standards_one(){
    $dbh = $this->connect();
    $data = array();
    for($x = 0; $x < (count($this->grades)); $x++){
    $stmt = $dbh->prepare("SELECT code, standard_one_id 
                           FROM standard_one 
                           WHERE grade_id = :grade_id 
                           ORDER BY standard_one_id");
    $stmt->bindParam(':grade_id', $this->grades[$x], PDO::PARAM_STR);
    $stmt->execute();
    $data[] = $stmt->fetchAll(PDO::FETCH_ASSOC);
    }
    $json = json_encode($data);
    return $json;
}