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Namespaces are a common idea in many
programming languages and

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PHP has had them since PHP 5.3.

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To some developers, they still feel a
little new.

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So let's take a look at how they work.

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The basic idea of using namespaces is to
ensure that two different classes,

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functions, or constants with the same name
do not cause conflicts.

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For example, if you try to define two
classes called client,

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then the second definition will cause a
fatal error,

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complaining that you can not redefine that
class.

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If instead, you put that class into a
namespace,

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you can refer to both of them differently.

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Let's take a look at how that works with
some code.

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Before we get started, pay no attention to
line four,

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as I'll explain about display errors later
on.

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So on line seven, we're including a
third-party piece of

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code that has been placed in the source
folder which handles HTTP interactions.

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On line eight, we're including another
third-party piece of

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code which will help us interact with the
Twitter API.

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Sadly, the developer of both the HTTP code
and the Twitter code has not

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used namespaces and instead declared the
classes into global namespace.

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Now we have these two client classes which
looks a little funny and

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will throw an error when we try and run
the preview.

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So you can see here, they've had trouble
redeclaring the class client

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because there's already a class called
client.

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If we have a look at the code we can see
how to fix this.

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We go into the source folder and inside
the HTTP folder and look at the Client.

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You can see here that there's no namespace
declaration.

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Now our namespace declaration is simply
the word namespace and then the name.

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We save that and we do the same thing to
Twitter and save that too.

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Now when we run this, PHP gives us a
different error.

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The complaint here is the class client
does not exist.

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Which is completely true.

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Now the class client is not being defined
in the global space.

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It has to be referenced with the
namespace.

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Let's get back to our workspace and try
that out.

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So if we remember the names of our
namespaces, which were HTTP,

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we type that in and we use a backslash to
de-reference it.

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Do the same for Twitter, and now we've
referenced our two different client

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classes correctly with their namespaces so
PHP knows where to find that code.

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We run this again.

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We can see that two objects, HTTPClient
and TwitterClient, have been created.

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We can further improve this code by using
auto-loading, and

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that's what we'll do in the next lesson.