Is there a PHP Sandbox, something like JSFiddle is to JS?

Yes, there are several PHP sandbox options available online. Some popular choices include:

• PHP Sandbox: http://sandbox.onlinephpfunctions.com/
• PHP Tester: https://phptester.net/
• PHP Fiddle: https://phpfiddle.org/
• Repl.it: https://repl.it/languages/php
• CodePen: https://codepen.io/ (has a PHP + HTML + CSS + JS option)

These sandboxes allow you to write, test and run PHP code in a web-based environment, similar to JSFiddle for JavaScript.