Pitfall of Defining Constants

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Pitfall of Defining Constants

The PHP define statement is really handy. I've used it to define all kind of constants. But recently I stumbled across a pitfall when I defined a constant name two different ways different if clauses. In the true clause, I defined it one way, while defining it another way in the false clause. The constant never changes. Two things I learned from this exercise.

Once a constant is defined, it can't be changed with another define statement.
All constants come into play as soon as the script is run; it doesn't matter if you put it in a scope bracket.

Knowing these constraints, I started developing my software more carefully, using scoped class variables, rather than using constants all the time. You might end up stepping on yourself quite often if you keep defining global constants.

Chieh Cheng
Wed, 23 Apr 2008 16:24:48 +0000

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