Is it bad to have a long name for an associative array in PHP?

Question

I have a function which must return one dimensional associate array, like $user_info[$index]=value where $index is a string which consist of

• user_id
• full_name
• photo_file_name

for example, my associative array could look like $user_info['user-123456789~~Bill Gates~~bill_gates.png']=$value. I need user_id, full_name and photo for another needs, in order to know whose value is this and what is his full name, etc.
So, the questions that has risen are following:

1. Is it OK to have such an array if to take into account performance of the application?
2. If it is bad (I think that it is bad idea) so how can I solve my problem in this case.

Additional info. This function retrieves user information into this associative array and returns this array. Further, my application stores it in a session in order to address it and retrieve information right from the session variable, not execute once again a query. And finally the reason I need one dimensional array is that I use a function array_diff where one of the arrays are $user_info array.
Note, Take into account that one user could have 1 or many values.

Any suggestions would be pleased.

Answer 1

You have a long key in an associative array.

I don't think it's a problem. If you wanted to shorten it you could hash your key-value and store the value with the hashed value.

That being said, have you asked yourself why you're using that schema? Might it be better to come up with a different data structure to suit your needs?

I'd be much more concerned with the amount of data (size of the array) that you're storing in the session variable. I think using the session to store data like this is a bad idea.

Answer 2

Any performance gained by concatenating that much information into a string is easily lost when you consider the maintenance/readabilty costs. Will that be easy to understand when the next programmer comes along and starts reading your code?

I would suggest an alternate data structure:

$user_info[$user_id] = array(
  'user_id'         => $user_id, // Redundant but helpful
  'full_name'       => $full_name,
  'photo_file_name' => $photo,
  'value'           => $value
);

Answer 3

So you are storing information (more than a key) into ~-separated array keys? It looks really ugly. It's probably not a performance problem though*.

Is it impossible to reimplement array_diff but modified for your needs?

*) I looked in the manual for information about how the keys are handled (balanced b-trees maybe?), but couldn't find anything satisfactory. There could actually possibly be a performance problem depending on the implementation, but PHP is usually good at this type of work.

Answer 4

On a point of terminology: in your example, the name of the associative array is $user_info. 'user-123456789~~Bill Gates~~bill_gates.png' is a key of the array. Arrays in PHP have keys and values.

To answer your question: No, there is nothing in particular wrong with having associative arrays whose keys are long strings; PHP doesn't particularly care. (The example you gave is not really a "long" string, anyway.)

However, the way you are doing things, as described, does sound like it could be improved. Consider adopting the array structure suggested by Mike B, or implementing a "user" class and returning an array of users from your function.