Instanceof and namespaces

问题

I am facing an unexpected behaviour trying to use the following:

$object instanceof $class

1/ PHP 'instanceof' keyword and namespaces work well together, as explained in the official doc.

2/ Sometimes, however, backslash escaping gives in to more subtle (obscure?) behaviour, as Ben kindly explained in this nice post.

Somewhere deep down in my code, y set a couple of dumps as follow:

var_dump($object, $class);
var_dump($object instanceof $class);

which gives me the following output when running my script:

class Tools\Tests\Entity\testObject#226 (2) {
  private $var_one =>
  NULL
  private $var_two =>
  NULL
}
string(36) "Tools\Tests\Entity\testObject"
bool(false)

The class of my first dump is strictly the same as the string in my second dump. However, my instanceof dump returns FALSE. Why ?

I played around with backslashes, with no luck. Maybe I messed up somewhere with namespaces ? The thing is I really don't know how to troubleshoot further down. What should I try ?

回答1:

You can test for instances using namespaces, but use the fully qualified class name.

For your test I would do this:

$class = "\\Tools\\Tests\\Entity\\testObject";
$object = new $class;
var_dump($object instanceof $class); //bool(true)

You can also test this way using single quotes and not worry about escaping your backslashes and save yourself a few keystrokes.

$class = '\Tools\Tests\Entity\testObject';
$object = new $class;
var_dump($object instanceof $class); //bool(true)

回答2:

I use simpler variant

var_dump($object instanceof \Tools\Tests\Entity\testClass);

回答3:

You should use ReflectionClass to avoid any execution or behaviours you have in\on this model. Read more aboit ReflectionClass to get more info about class\model we checking. http://php.net/manual/en/class.reflectionclass.php

foreach ($this->modelNamespaces as $namespace) {
    $reflectionClass = new \ReflectionClass($namespace);

    if ($reflectionClass->implementsInterface('common\models\FieldsInCollectionInterface')) {
        // class is implemented by FieldsInCollectionInterface
    }
}

来源：https://stackoverflow.com/questions/23807992/instanceof-and-namespaces

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instanceof