This code sets the target directory for the uploaded file and gets the file name from the file input element. It then checks if the file is an image using the getimagesize() function, and sets the uploadOk variable to 1 or 0 depending on the outcome. The package library used for this functionality is the PHP file upload library, which is included in the core PHP package. There are also several third-party packages available for handling file uploads in PHP, like the Symfony FileUploader component or the Laravel Filesystem package.