Pergunta de entrevista da empresa Zycus

In 2nd and 3rd round they asked questions based on javascript and PHP 1. Use of const, var, let 2. What is callback function. difference between call back and promises. 3. What are hooks and how to use them. 4. Difference between class,library, helper. 5. List some basic helpers. 6. database setting questions 7. PHP mail function 8. What is API and what are uses. 9. What projects have worked on.