Question about including files and server load

I just started working with a new company and they handed me some of their php code for me to look over. I noticed that they have a TON of include files being called into their scripts. For example, instead of having one file called functions.php and then having all their functions in that one file they have put each function into it's separate file and then have a define_functions.php file that creates each function. However, within the function itself it declared something like this: function xyz($abc) { return include(xyz_func.php); } function abc($xyz) { return include(abc_func.php); } I was wondering isn't this putting a bigger load on a server by including so many files for each function? Also, I was wondering what everyone's opinion was on this approach in terms of maintenance. Do you think it's better practice to put all your functions in one file or do it in this manner? thanks for any input! jay