Question: I'm searching for following issue i have.
The class file names of our project are named logon.class.php
But the interface file for that class is named logon.interface.php

My issue i have is that when the autoload method runs I should be able to detect if it is a class call or an interface call.

```
<?php 
function __autoload($name){
    if($name === is_class){
        include_once($name.'class.php');
    }elseif ($name === is_interface){
         include_once($name.'interface.php');
    }
}
?>

```

Answer: 
You can use [ReflectionClass::isInterface](http://au.php.net/manual/en/reflectionclass.isinterface.php) to determine if the class is an interface.

```
$reflection = new ReflectionClass($name);

if ($reflection->isInterface()){
  //Is an interface
}else{
  //Not an interface
}

```

In your case, you would probably have to use `file_exist` first on `$name.interface.php` and `$name.class.php` to determine if they exist, require the one that exists, then check if it's an interface.

However, my opinion is that this might cause problems down the track. What if you have `MyClass.class.php` and `MyClass.interface.php`?
To avoid class name clashes you can use namespaces. Check The PSR-0 specifications.

Also check this [post](https://stackoverflow.com/questions/928928/determining-what-classes-are-defined-in-a-php-class-file/11114724#11114724). If you read the contents of the file before including it, you can tokenize it and figure if the file contains an Interface or a class, without actually loading the class/interface. Keep in mind that interfaces and classes can't have the same name 

Note: Using this method you can actually change the name of the interface at runtime (before loading the class, although that does seem very good practice)