What is the correct way to check if library/helper/core files are loaded in CodeIgniter

I'm using Codeigniter 2.

Appreciate if someone could show the correct way to check if the following files :

• library file is loaded?
• helper file is loaded?
• config file is loaded?
• model file is loaded?
• third_party file is loaded?

You can use the native PHP function class_exists() to determine if the class has been defined, before calling it. In same regard, using method_exists() will check if class method exists.

Since helpers are collection of function, not methods, checking can be done using function_exists().

if (class_exists('Library')) 
{
    $this->library->myMethod();
}

For further info please refer to

http://php.net/manual/en/function.class-exists.php.

http://us.php.net/manual/en/function.method-exists.php