Replacing a value in an associative array?

Question

I have this:

foreach ($books as $book)
{
    $catname = get_category_name($book['category']);
    $book['category'] = $catname;
}
print_r($books);

Right now, $book['category'] represents an integer value, which references the ID of a row in a category table of the database (eg ID 1 = Fiction). As you can guess, get_category_name($id) takes an ID and finds the correct row, and returns the name of the category. The function works correctly, and if i print_r($catname) in the foreach it prints the names of the categories, like it should.

I have an associative array called $books that gets filled from every row in the book table in the database. What I want to do, is take the category integer value of each book element and use get_category_name($id) to replace that integer value with the actual category name.

The problem I am having is that I cannot replace the integer value that already exists at $book['category'] with the actual category name which resides in $catname . When I use print_r($books) to see if the changes were made in the foreach , they confirm the changes do not get made.

How can I fix this?

Answer 1

I think you want something like this?

foreach ($books as &$book)
{
    $catname = get_category_name($book['category']);
    $book['category'] = $catname;
}
print_r($books);

Notice the &$book.

Answer 2

You either use foreach($books as &$book) and edit $book . This way you have a reference to the real book element inside the array in stead of a copy of it. Beware that if you want to do this multiple times on the same array, you will need to reset the array each time after use. See: http://nl1.php.net/reset

Or you use foreach($books as $key=>$value) and edit $books[$key] . This way you get copies of the books and their keys. But you then use the key on the original array.

Answer 3

THe problem is that in fact you do not change $books but $book , that is why you cant see changes in $books . Possible solution:

foreach ($books as $booksId => $book) //$booksId will contain current index in $books
{
    $catname = get_category_name($book['category']);
// now you can change correct index in $books:
    $books[$booksId]['category'] = $catname;
}

Edit: @Cardinal solution with refference is also correct.