Best way to include phar file

Dear All,

I need to incorporate an api into my application. I am provided with a single phar file. I am not familiar with this kind of file and have no idea on how to include this into my application.

They said that I only need to add this line

require '/path/to/api-sdk-php.phar';

Where would be the best practice to add this line? Inside the method (function)? In the PHP file? or in the index.php in the root file?

Thank you in advance.