How to check the existence of a namespace in php

Question

I have a php library https://github.com/tedivm/Fetch and it uses Fetch namespace and I would like to check its existence in my script.

My script code:

// Load Fetch
spl_autoload_register(function ($class) {
    $file = __DIR__ . '/vendor/' . strtr($class, '\\', '/') . '.php';
    if (file_exists($file)) {
        require $file;

        return true;
    }
});

if (!class_exists('\\Fetch')) {
  exit('Failed to load the library: Fetch');
}
$mail = new \Fetch\Server($server, $port);

but this message is always displayed. But the library is fully working.

Thanks in advance for any help!

Solution 1

You need to use the entire namespace in the class_exists I believe. So something like:

class_exists('Fetch\\Server')

Solution 2

As George Steel wrote, it is impossible to check for a namespace. This is because a namespace is not something that exists; only structures exist within namespaces. See below example:

namespace Foo;

class Bar {
}

var_dump(class_exists('Foo')); // bool(false)
var_dump(class_exists('Foo\Bar')); // bool(true)

Solution 3

You can't check directly for the existence of a particular namespace, i.e. you'd have to class_exists('Fetch\\SomeClass'). See this question too: is it possible to get list of defined namespaces

Comments

[ars265]

sorry, no preceding backslash, updating the answer

[ars265]

It's a nice ability to do this but can be very (processor) time consuming if you have many classes, which is where you would be most likely to use namespaces.

[DrLightman]

Double slashes are not needed in single quote string. class_exists('Fetch\Server')

[Bitterblue]

The answer is either strange or incomplete. Please add a note that you need to check the existance of a class in that namespace. So we can't check the namespace alone.