php static variable initialization doesn't make sense here

Question

I am talking about Common.php file of CodeIgniter framework(system/core folder).

// not required to answer the question though!

I have been going through the code and couldn't make sense of these particular lines at start of load_class function.

static $_classes = array();

// Does the class exist?  If so, we're done...
if (isset($_classes[$class]))
{
    return $_classes[$class];

My doubt specifically is, isn't it pointless to declare a variable to an empty array, and immediately check if some key exists in that array? or am I missing something related to static keyword?

drew010 · Accepted Answer · 2012-08-11 19:36:52Z

4

The static modifier in front of that variable means that the value of $_classes persists after each function call.

So the first time that function is called, $_classes does not yet exist so it gets created as an empty array.

Since its empty, the class doesn't exist, so it gets loaded and put in the $_classes variable.

Now when the function terminates, because it is static, it does not get cleaned up, and its value persists.

The next time the function is called, PHP knows it already exists so it is not initialized as an empty array, it still contains what it had the last time the function was called.

See using static variables for more information.

answered Aug 11, 2012 at 19:36

drew010

70.3k11 gold badges144 silver badges174 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Prasanth Over a year ago

I haven't ever used static in php! I guess there is lot of php to master. Thank you.

Collectives™ on Stack Overflow

php static variable initialization doesn't make sense here

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related