Code speaks better than words:
namespaces.php:
<?php
namespace foo;
use foo\models;
class factory
{
public static function create($name)
{
/*
* Note 1: FQN works!
* return call_user_func("\foo\models\$name::getInstance");
*
* Note 2: direct instantiation of relative namespaces works!
* return models\test::getInstance();
*/
// Dynamic instantiation of relative namespaces fails: class 'models\test' not found
return call_user_func("models\$name::getInstance");
}
}
namespace foo\models;
class test
{
public static $instance;
public static function getInstance()
{
if (!self::$instance) {
self::$instance = new self;
}
return self::$instance;
}
public function __construct()
{
var_dump($this);
}
}
namespace_test.php:
<?php
require_once 'namespaces.php';
foo\factory::create('test');
As commented, if I use the full-qualified name inside call_user_func()
it works as expected, but if I use relative namespaces it says the class was not found – but direct instantiations works. Am I missing something or its weird by design?
You have to use the fully qualified classname in callbacks.
See Example #3 call_user_func()
using namespace name
<?php
namespace Foobar;
class Foo {
static public function test() {
print "Hello world!\n";
}
}
call_user_func(__NAMESPACE__ .'\Foo::test'); // As of PHP 5.3.0
call_user_func(array(__NAMESPACE__ .'\Foo', 'test')); // As of PHP 5.3.0
I believe this is because call_user_func
is a function from the global scope, executing the callback from the global scope as well. In any case, see first sentence.
Also see the note aboveExample #2 Dynamically accessing namespaced elements which states
One must use the fully qualified name (class name with namespace prefix).
Answer:
In current versions of PHP, the way you have it is the way it is — when using a string to reference a classname, it needs to be fully qualified with it’s complete namespace. It’s not great, but that’s the way it is.
In the forthcoming PHP v5.5, they will include a feature to address this, by providing a new Classname::class
syntax, which you can use instead of putting the FQN classname in a string.
For more info on this, please see the relevant PHP RFC page here: https://wiki.php.net/rfc/class_name_scalars
Your code would look something like this:
return call_user_func([models$name::class,"getInstance"]);
That may not be exact; I don’t have a copy of 5.5 to test with to confirm. But either way, the new syntax will make things a lot better for use cases like yours.
Tags: phpphp