PHP namespaces : \My\Namespace or My\Namespace?

Question

• My\Namespace
  • \My\Namespace

So, which one should I use, I see the php documentation uses mostly My\Namespace.

But it is said that \My\Namespace is better, because non ambiguous, whereas My\Namespace could be resolved as \RandomNamespace\My\Namespace.

I've started to wonder about this after reading there is an issue in Doctrine 2 about this : "Please replace 'Doctrine\XXX\YYY' with '\Doctrine\XXX\YYY' in code and document"

So, do you have any more information about this ? Thanks

Answer 1

This is no different than using relative vs absolute file/uri paths and will come down to preference. However, unlike absolute paths, I agree with the less ambiguous \My\Namespace because it will never break, where relative namespaces could.

Namespace aliases, via use add to the abiguity of relative namespace names. For example, I can say: use \PDO as YourMom and later call YourMom within the code. Is it \PDO, \YourMOM, or YourMom that it is being called? Obviously the alias wins and is resolved to \PDO, assuming there is no conflict, but it makes code hard to follow.

Edit

Code example to prove abiguity is possible. Make sure you see the global fallback applied if a namespace is unqualified.

As mentioned by @netcoder, it is impossible to be abiguous during the declaration of a namespace. Thus, namespace My and namespace \My (or swap any other namespace declaration below) are 100% identical as and declaration fully qualifies a namespace.

namespace My
{
}

namespace My\Other
{
    use Bob; // Resolves to \My\Other\Bob
}

namespace My\Other\NS
{
    use \My\Other as Other;
    use Other\NS as Duh; // This resolves to \My\Other\NS
}

namespace My\Other\Bob
{
    use Other\NS as Duh; // This resolves to \Other\NS becuase the namespace doesn't exist inside \My\Other\Bob
}