Constants can be handy when used correctly. Unfortunately, there's some small issues you might want to watch out for. Ben Ramsey discovered one while working with another's code - an undefined constant acting like a string.

From the I-noticed-this-one-day-while-looking-at-a-co-worker's-code department comes a tale about the use of undefined constants in PHP—and relying on this twisted "feature" to make an application function properly.

He relays a little story about the errant code and noticed the constant that wasn't defined and how PHP was treating it like a string. After searching the manual, though, he finds a reference related to the situation showing that it will only throw an E_NOTICE when this happens.

Ben's suggestion is for a bit more than that - at the very least an E_WARNING. Having it down at E_NOTICE won't be seen by most with the default php.ini, and he gives an example as to why it's a bad thing (passing this string/constant into a function and how it handles it).

Constants can be handy when used correctly. Unfortunately, there's some small issues you might want to watch out for. Ben Ramsey discovered one while working with another's code - an undefined constant acting like a string.

From the I-noticed-this-one-day-while-looking-at-a-co-worker's-code department comes a tale about the use of undefined constants in PHP—and relying on this twisted "feature" to make an application function properly.

He relays a little story about the errant code and noticed the constant that wasn't defined and how PHP was treating it like a string. After searching the manual, though, he finds a reference related to the situation showing that it will only throw an E_NOTICE when this happens.

Ben's suggestion is for a bit more than that - at the very least an E_WARNING. Having it down at E_NOTICE won't be seen by most with the default php.ini, and he gives an example as to why it's a bad thing (passing this string/constant into a function and how it handles it).