The request lifecycle.
WHAT HAPPENS
A request arrives at the web server The server passes it to PHP PHP executes the relevant file The output is returned The process ends
WHAT MATTERS ABOUT THAT LAST POINT
Each request starts fresh.
Nothing persists between requests unless you store it somewhere.
WHAT THAT MEANS
Variables do not survive State must be held in a session, a database, a cache or a file
WHY THAT DESIGN
It makes applications simple to reason about and easy to scale.
WHAT IT COSTS
Everything must be loaded again each request.
WHAT THAT IMPLIES
Loading less, and caching what is expensive, matters considerably.
WHAT SESSIONS DO
Associate data with a visitor across requests, using an identifier.
WHAT TO UNDERSTAND
Where sessions are stored, and that they consume space.
WHAT ELSE TO KNOW
Time limits apply to execution, and memory limits apply per request.
Both are configurable within your plan's bounds.
