some basic interview questions asked against php developer

1-explain how session work?
2-what are some of the big changes php has gone throught ?
3-what is polymorphism?
4-name three visibility keyword in php
5-what is difference between $_get and $_post?
6-how object are passed by value or reference?
7-what is difference between $ and $$?
8-how triggers are used in php mysql?
9-what is mvc in php and name some frameworks?
10-what are some magic methods in php , how we can use them?