That's at best semantic nit-picking. You cannot write a useful C program without using the standard library or re-implementing (parts of) its functionality yourself. If for some reason having functions available that you don't use bothers you, you can still easily disable most of them by not loading any extensions; and if it's really a big issue to have the 'standard' functions in php available, you can compile php to not include them. If this is the best example of why php isn't like C, they are actually very similar...
What about hundreds or thousands of inconsistently named built-in functions?
C doesn't really have built-in functions, just a standard library that you don't have to load if you don't like it.