问题
When declaring the following namespace:
<?php
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?
回答1:
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:
<?php
namespace Example\V_3000;
回答2:
Note: Special character cannot be used. The only special character I have found that works is the underscore (_). For example if you want a folder for version 3.0.01, then do the following:
<?php
namespace Example\v3_0_01;
来源：https://stackoverflow.com/questions/33875380/can-a-namespace-start-with-a-number-in-php