There are plenty of places where PHP doesn't allow whitespace currently.
The most comparable example is between namespace separators:
Ns \ bar();
Ns \ SOME_CONST;
are both syntax errors.
`MyClass::bar()` and `MyClass::SOME_CONST` are often used in place of
`Ns\bar()` and `Ns\SOME_CONST` because the former invokes the autoloader in
a way the latter does not. My gut tells me they should behave the same way
with respect to whitespace, too.
In some situations PHP _does_ treat the identifier "Foo::bar" differently
to "Foo :: bar":
class A {
public static function b() {
return 5;
}
}
echo "A::b"(); // works
echo "A :: b"(); // fatal error
