what is the difference between case sensitive and case insensitive in this basic progm. i dont see much different in output

Answer 1

Case sensitive means php and Php are different whereas case insensitive means they are same.Normally in the programming languages variables and keywords are case sensitive.

Answer 2

There is a valid reason why some code works ony when used in a certain case. Take constant for example. It is best to follow a standard and stick to it. like any language codes will become your second nature. and when time comes it is very difficult to change your style.

Answer 3

I think the basic reason why there's no visible difference in the output is because the codes are the same as one word. It's pretty much not about the value but about the name.
In case sensitive,
echo MSG
and
echo msg
would definitely not give the same output. But they would if it was case insensitive.