Which of the following PHP function is commonly used when handling authentication via PHP?
i) header()
ii) footer()
iii) inset()
iv) isset()
a) i) and iv)
b) ii) and iv)
c) ii) and iii)
d) i) and iii)

Answer: a
Explanation: The function isset () is used to check whether a variable is set or not and the function header() sends a raw HTTP header to a client.