PHP spl_autoload_register

Question

I am trying to take advantage of autoloading in PHP. I have various classes in different directories, and so I have bootstrapped the autoloading as follows:

function autoload_services($class_name)
{
    $file = 'services/' . $class_name. '.php';
    if (file_exists($file))
    {
        require_once($file);
    }
}

function autoload_vos($class_name)
{
    $file = 'vos/' . $class_name. '.php';
    if (file_exists($file))
    {
        require_once($file);
    }
}

function autoload_printers($class_name)
{
    $file = 'printers' . $class_name. '.php';
    if (file_exists($file))
    {
        require_once($file);
    }
}

spl_autoload_register('autoload_services');
spl_autoload_register('autoload_vos');
spl_autoload_register('autoload_printers');

It all seems to work fine, but I just wanted to double check that this is indeed considered acceptable practise.

Answer 1

It's okay, but if these are just folders below a certain folder, e.g.

/library
    /JonoB
        /services
        /vos
        /printers

you might want to consider adding these to your classnames, e.g.

JonoB_Services_Foo, JonoB_Vos_Bar, JonoB_Printers_Baz

and then split the $classname by the underscore and take each part as folder name. This is similar to PEAR class name convention. This way you would only have one loader.

Instead of PEAR convention style classnames, you can also use namespaces (autoload example), but be aware that these require PHP5.3 which is not widely available on shared hosting yet. And your application won't be backwards compatible with PHP<5.3 then (if that's an issue).

Answer 2

... or just use namespaces ...

Answer 3

Sure, looks good. The only thing you might do is register them in the order they're most likely to hit. For example, if your most commonly used classes are in services, then vos, then printers, the order you have is perfect. This is because they're queued and called in-order, so you'll achieve slightly better performance by doing this.

Answer 4

Good advice from all the other answers.

Let me add that each autoloader should first check if it even cares about the class being passed in, and return immediately if not.

So if you do as Gordon suggests and add a prefix to each class, then for Services_Foo the autoloader autoload_services() should see if "Services_" is the first substring of $class_name, and if not return false immediately to save on any further processing, especially filesystem checks.

Answer 5

You could use:

set_include_path(get_include_path() . PATH_SEPARATOR . './services' . PATH_SEPARATOR . './vos' . PATH_SEPARATOR . './printers');
spl_autoload_register();

Using spl_autoload_register without arguments will register spl_autoload which will look for the class name in the directories of the include path. Note that this will lowercase the class name before looking for it on the filesystem.