Does PHP parse entire files or only on demand?
<p>If I write an entire website in a single App class PHP file and include it in every page, then from each page, I call only the related functions and render the page (separate template files) from the App class.</p>

<p>Does PHP actually read the entire script or does it just try to search for only the functions being called? This is with regards to large apps, load times and bandwidth.</p>
