PHP Fatal error: Class 'Espo/Core/Hooks/Base not found in?

[worldmiros]

I'm using phpstorm, and when I run a file, specifically Quote/QuoteItem.php, I get an error stating, "PHP Fatal error: Class 'Espo/Core/Hooks/Base' not found in".
ex. Class QuoteItem extends \Espo\Core\Hooks\Base
I'm trying to see if I modify code in any matter to my desire, but nothing happens. So when I try run the file, I get the fatal error above. Not sure why I'm getting the error.

[yuri]

You can't run php files. You can run only entry points. Index.php

[worldmiros]

@yrikuzn, so if I were modify any part of the code in Quote/QuoteItem.php file, nothing will change on the interface?

[worldmiros]

hi yuri, i need to bring the work to the customer, and give me a quotation for your help. i need to understand how to customize espo.