Why do PHP Array Examples Leave a Trailing Comma?

Question

I have seen examples like the following:

$data = array(
   \'username\' => $user->getUsername(),
   \'userpass\' => $user->getPassword(),
   \'em         


        

Answer 1

Why do PHP Array Examples Leave a Trailing Comma?

Because they can. :) The PHP Manual entry for array states:

Having a trailing comma after the last defined array entry, while unusual, is a valid syntax.

Seriously, this is entirely for convenience so you can easily add another element to the array without having to first add the trailing comma to the last entry.

Speaking of other languages: Be careful with this in JavaScript. Some older browsers will throw an error, though newer ones generally allow it.

Answer 2

This is a good practice when defining array on multiple lines. It's also encouraged by ZendFramework's coding standards:

When using this latter declaration, we encourage using a trailing comma for the last item in the array; this minimizes the impact of adding new items on successive lines, and helps to ensure no parse errors occur due to a missing comma.

Answer 3

Because it keeps entries uniform.

If you've had to swap the order, or add or delete entries, you know being able to leave a trailing comma is very convenient.

If the last element cannot have a comma, then you end up having to maintain the last comma by modifying entries. It's a pointless exercise and a waste of time and finger strokes because the intent of swapping or modifying entries is already accomplished.

By allowing a trailing comma on the last element, it frees the programmer from having to tend to this annoying and fruitless detail.

Answer 4

I can't speak for other people, but I usually leave a trailing comma in my code. I do so because if/when I later add to the array, I do not have to worry about missing out a comma due to forgetting to add a comma to what was previously the last line.