sharing library between Multiple Applications with one CodeIgniter Installation

You shouldn't put anything in the `system` folders. Leave that for CodeIgniter otherwise your changes will get overwritten whenever you upgrade the CI core.

Instead, for common libraries, create a new folder, and add that folder as a Package in both of your applications. You can have this path autoloaded by adding it to the autoload.php config file. By default it will load APPPATH/third_party but you can always replace that if you don't use it.

Code:

$autoload['packages'] = array(FCPATH.'common');

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