PHP5 static keyword and usage

The static keyword is known to be a free agent.

You can declare a method "static" either by writing:

protected static function foo() {
// lots of self:: code in here
}

Or:

static protected function bar() {
// lots of self:: code in here
}

I just came across code that read:

static protected static function foobar() {
// lots of self:: code in here
}

Surely it's a typo from the original author, but why is PHP accepting this as a valid statement?

UPDATE The version in question is PHP 5.2.16. I just confirmed, this is valid too:

static static static public static function foobar(开发者_如何学JAVA) {
// lots ...
}

That appears to be a bug in previous versions of PHP which has been fixed. Testing it in PHP 5.3 yields

Fatal error: Multiple static modifiers are not allowed

EDIT: thanks to Matt Gibson for the find, this was indeed a bug that was fixed somewhere in the PHP 5.3 branch.