Question

I have 2 tables: questions, answers.

• questions has the fields: questionId, title, category,
  correctAnswerID, url
• answers has the fields: answerId, questionId, text

I have this function:

$result = query("SELECT * FROM questions INNER JOIN answers ON questions.questionId=answers.questionId");

it returns the questions 4 times, and every time with different answer.
I want an array that contains an array of questions, and every question will has an array of related answers.

Every question has 4 possible answers, and every question has the correct answer ID.

Thanks in advance.

Answer 1

MySQL cannot return such a multi-dimensional array natively, only a 2 dimensional array where level one is the rows, and level-two are the columns.

You’ll have to iterate the result set and build the array yourself.

In PDO, you’d do something like this:

try {
    $pdo = new PDO("mysql:host=localhost;dbname=test", "root", "");
    $pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);

    $stmt = $pdo->query("SELECT * FROM questions INNER JOIN answers ON questions.questionId=answers.questionId");

    $result = array();

    while ($row = $stmt->fetch(PDO::FETCH_ASSOC)) {
        foreach ($row as $column => $value) {
            if ($column != "answerId") {
                $result[$row["questionId"]][$column] = $value;
            }
        }
        $result[$row["questionId"]][$row["answerId"]] = $row["text"];
    }
}
catch (PDOException $e) {
    //Todo: Error Handling Here
}

Which gives me the following result (yours would probably look different):

array (size=2)
  1 => 
    array (size=9)
      'questionId' => string '1' (length=1)
      'title' => string 'b' (length=1)
      'category' => string 'letters' (length=7)
      'correctAnswerID' => string '2' (length=1)
      'text' => string 'd' (length=1)
      1 => string 'a' (length=1)
      2 => string 'b' (length=1)
      3 => string 'c' (length=1)
      4 => string 'd' (length=1)
  2 => 
    array (size=9)
      'questionId' => string '2' (length=1)
      'title' => string 'd' (length=1)
      'category' => string 'letters' (length=7)
      'correctAnswerID' => string '8' (length=1)
      'text' => string 'd' (length=1)
      5 => string 'a' (length=1)
      6 => string 'b' (length=1)
      7 => string 'c' (length=1)
      8 => string 'd' (length=1)