PHP Unit 3 Question

1. What is cookie and session explain in detail?
2. Explain GD library usages in PHP
3. Explain any seven server variable of php.
4. Explain Sending Email using mail() or smtp().
5. What is AJAX.Explain how it works.
6. Explain regular expression of php.
7.  Explain JSON Functions(json_decode,json_encode)
8. Explain JSON Serializable.