Question

im trying to understand the framework structure in CodeIgniter and i have just started and came up with this little misunderstanding .

so can somebody please help me under stand the following :-

1- why do they use a reference to pass an instance of the class … i mean why not just a simple variable ?

2- and why does the function store the name of the class in an array instead of a “string variable” (please dont judge my php terms as im the worst at it ).. ?!

static $_classes = array();
                   ^^^^^^^ this cloud be just ("") or am i missing something

here is the function so you wont go looking for it .

function &load_class($class, $directory = 'libraries', $prefix = 'CI_')
    {
        static $_classes = array();

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

        $name = FALSE;

        // Look for the class first in the local application/libraries folder
        // then in the native system/libraries folder
        foreach (array(APPPATH, BASEPATH) as $path)
        {
            if (file_exists($path.$directory.'/'.$class.'.php'))
            {
                $name = $prefix.$class;

                if (class_exists($name) === FALSE)
                {
                    require($path.$directory.'/'.$class.'.php');
                }

                break;
            }
        }

        // Is the request a class extension?  If so we load it too
        if (file_exists(APPPATH.$directory.'/'.config_item('subclass_prefix').$class.'.php'))
        {
            $name = config_item('subclass_prefix').$class;

            if (class_exists($name) === FALSE)
            {
                require(APPPATH.$directory.'/'.config_item('subclass_prefix').$class.'.php');
            }
        }

        // Did we find the class?
        if ($name === FALSE)
        {
            // Note: We use exit() rather then show_error() in order to avoid a
            // self-referencing loop with the Excptions class
            exit('Unable to locate the specified class: '.$class.'.php');
        }

        // Keep track of what we just loaded
        is_loaded($class);

        $_classes[$class] = new $name();
        return $_classes[$class];
    }

Answer 1

The key is the static keyword before $_classes = array();. This makes the $_classes array hold it’s value in between multiple calls to the function. Basically they use it as a local cache for the instantiated classes. For this purpose a string won’t work.

See more about the static keyword in the manual.

As for the reference returning, i think that’s php4 baggage, CI was supported on php4 until 2.x. You might find this blogpost helpful to see what was changed from php4 to php5.