Strange phenomenon, am I alone?

[eluser]ixxalnxxi[/eluser]
This problem happened again just now. I defined a serialized array into a constant then attempted to (for about 10 minutes) echo its its length with count() in my controller, however it simply did not work. After echo-ing a value with a specific key successfully and simply undoing my code to the same previous not-working state, the size of the array now started to echo.

I did now know caching was also an issue when working with server side scripting. What can I do to ensure this doesn't happen?