Fix outdated JWT dependency and apply PSR standards

[ataBarzegar79]

Hi there,

While reviewing the PHP examples in your repository, I noticed that Composer flagged the JWT package version as expired.

Changes included:

1. Updated Dependencies: Bumped the JWT package to a supported version.
2. Code Style: Refactored the code to satisfy PSR standards.
3. Added a return value for the single request function, which is required since PHP 7.4

I intentionally avoided adding architectural layers to keep the example accessible for developers of all skill levels. However, if you are open to it, I would be happy to submit a follow-up update to further improve readability.