Are PHP functions case sensitive?

Question

I was digging through some code, and I found some calls to mySQL_fetch_array. Is PHP case sensitive about function names? I recall reading this somewhere but can't seem to find any reference to it.

Answer 1

I am quoting from this:

Note: Function names are case-insensitive, though it is usually good form to call functions as they appear in their declaration.

So, its looks like user-defined functions are not case-sensitive, there was a vote for making functions/objects under PHP5 case-sensitive.