When would you throw a DomainException in PHP?

Question

I was going through the list of predefined Exceptions in PHP and I noticed the DomainException. Anyone know what does DomainException mean? Does it mean failed data model valida

Answer 1

The description of RangeException is a bit more helpful:

Exception thrown to indicate range errors during program execution. Normally this means there was an arithmetic error other than under/overflow. This is the runtime version of DomainException.

I think it is applicable to non-arithmetic too, e.g. see this user comment.

For example, if you expect a value to be in the set {'jpeg', 'png', 'gif', 'bmp'} and you receive something else like 'foo', it's a good candidate for a DomainException (logic) / RangeException (runtime). I'm pretty sure you could think of many other use cases.

Also, I just found this useful article, which provide more thorough explanations than php.net: How to use built-in SPL exception classes for better error handling

Answer 2

There's a pretty hilarious discussion here about how no one seems to know what is means:

http://bugs.php.net/bug.php?id=47097

From the end of that link:

Domain means data domain here. That is a DomainException shall be thrown whenever a value does not adhere to a defined valid data domain. Examples:

• 0 is not in the domain for division.
• Foo is not in the domain for weekdays.

The first is different from out of range and alike, but you could use InvalidParameter in case it is actually a parameter to the function that performs the division. If it is a value calculated inside the function prior to executing the division and then a pre-conditon check throws instead of executing the division, then it becomes a DomainException.

Answer 3

This kind of exception should be used to inform about domain errors in mathematical sense.

See domain of a function.

For example, the square root function will only be defined for positive numbers (unless you're using complex numbers...)