How to get the line and file where a php function is defined?

i want to inspect and analyse a function in php, but I don't know where the function is defined (eg. line and file) and I also don't know the headerfiles, because I don't need them in php. The function I want to analyze is 'include()'. How I can get the source code or file where the function is defined and how I can get the source of other well known functions (eg. print, echo)?