Just wondering if someone could educate me about best practices regarding PHP and server resources. Specifically, are there recommended thresholds for:

• PHP file sizes
• The number of file includes
• The number of queries executed per page
• The types of functions that reduce the server load vs the types that increase it

I realize there aren't necessarily clear cut answers and obviously, the smaller sizes and fewer number of requests are better. I'm just curious if you have any standards you follow and what they are if you do.

What for? If you at least use mysql database your delays on connecting, sending queries and reading results will be much, much greater than those milliseconds you would save optimizing your php code. Of course you can make any code one byte shorter and one cpu tick faster, but is it really necessary to fight for extra milliseconds if your sql query executes 0.5 seconds? In this case you should optimize your tables and your queries instead. And if the problem of saving milliseconds is really actual, if e.g. you are having 1000 hits/second still it should not be optimized by means of php because it is called "highload" and you should use quite other solutions like light-weight frontend webserver serving static files.