Can a namespace start with a number in PHP?

When declaring the following namespace:

namespace Example\3000;

I got this error:

Parse error:  syntax error, unexpected '3000' (T_LNUMBER), expecting identifier (T_STRING) in [...]

So I wondered whether a namespace in PHP may start with a number?

Answer

No, it must not. It must start with a letter.

It took me a while to find this in a comment on PHP.net.

To use numbers e.g. for versioning it is necessary to prepend letters, e.g. like in the following:

namespace Example\V_3000;