Php file question

Just a question for rules regarding php file structure… In what circumstances is it best to create a new php file?

Do most dynamic php websites have multiple php files, one per dynamic html page for example or is it better to have lots of php functions lumped into the one php file?

Also, Im reading a book which says that “as a php application executes it moves from one web page to another”. Can someone explain this for me?

Im new to all this stuff - fascinating but challenging for a noob!

Cheers

I personally have a general file with general functions i might need in other projects.

For any specific project that has its own functions i have a file called localfuncs.php and put them in there.

The actual project code itself i tend to break up into different files but that stems from my early days when a missing { would have me hunting for hours even in notepad++. Truth be told i could probably just put everything in one large file now but even then it could be a pain trying to locate things so i personally recommend keeping stuff seperate.