PHP Namespace Syntax: What is the Difference with Braces vs. without Braces?

Question

PHP offers two syntax for declaring namespaces. You can use a namespace with no braces or with braces as seen below.

Without Braces

namespace foo/bar;
class Any{}

With Braces

namespace foo/bar {
   class Any{}
}

Is there a difference in the functionality or behavior of these two ways of using namespaces or do they both work/function the same way?

Answer 1

There are different reasons for each case, there is a good example on the PHP site.

The reason you'd use curly brackets around a namespace is if there are multiple namespaces in the one file or where you need to have global non-namespaced code in the same file as code that is contained within a namespace.

Also if there are multiple namespaces in one file, the non-bracketed syntax is allowed as well.

As per php guidelines this is not recommended and if you can, just keep it to one namespace per file.

Answer 2

In the first variant, you can only use one namespace per file, whereas the second allows for multiple namespaces. They can be used interchangeably and may occur multiple times in a single file to define multiple namespaces. The only reason to use curly braces is in this case:

namespace {
    // code is in global scope
}

Other than the above example, a potential downside of having multiple namespaces in a single file is autoloaders that use the directory and file names to resolve classes to load; it's therefore not recommended to have more than one namespace per file, unless you're combining multiple script files into one.