Reorder array from mysql query - php

Question

I have an array returned from MYSQL query with 2 LEFT JOINs.
Question is: "Is there another way for writing the code below?". I got the code but I want a more clear way of it just to understand what happens inthere.
CODE:
$result = array();
while ($resultArr = mysqli_fetch_assoc($booksAndAuthors)) {
$result[$resultArr['book_id']] ['book_name'] = $resultArr['book_title'];
$result[$resultArr['book_id']] ['author'][] = $resultArr['author_name'];
print_r($result);
}

Answer 1

With the extract() function you can make the data in the result into variables. I have put the example below inside a function, so they will be local variables.
function getBooksAndAuthors($queryResult)
{
while ($data = mysqli_fetch_assoc($queryResult))
{
extract($data);
$BooksAndAuthors[$book_id] = array('book_name' => $book_title,
'author' => $author_name);
}
return $BooksAndAuthors;
}
This makes the code a lot more readable. You will, of course, have to know which columns there are in your database table. I also left out the extra '[]' for the author.

Answer 2

Here's how I recommend writing it, because I don't think you should depend on automatic creation of intermediate arrays.
$result = array();
while ($row = mysqli_fetch_assoc($booksAndAuthors) {
$bookid = $row['book_id'];
if (!isset($result[$bookid])) {
# First time we see this book, create a result for it
$result[$bookid] = array('book_name' => $row['book_title'],
'author' => array());
}
# add this author to the result entry for the book
$result[$bookid]['author'][] = $row['author_name'];
}
It's essentially equivalent, but I think it also makes the logic clearer.