How to check if a class is a Doctrine entity?

Courtesy Stof on the doctrine-dev mailing list:

return ! $em->getMetadataFactory()->isTransient($className);

I'll add that this method considers proxies (returned by the EntityManager as part of the lazy loading strategy) as transient; so if you're testing objects, don't blindly use get_class(), be sure to test first:

$object instanceof \Doctrine\Common\Persistence\Proxy

Working implementation:

use Doctrine\Common\Persistence\Proxy;
use Doctrine\ORM\EntityManager;

function isEntity(EntityManager $em, string|object $class): bool
{
    if (is_object($class)) {
        $class = ($class instanceof Proxy)
            ? get_parent_class($class)
            : get_class($class);
    }

    return ! $em->getMetadataFactory()->isTransient($class);
}

As an addition to Benjamin his answer...
If you know for sure that you are handling doctrine entities, but you are not sure whether you have a proxy or a instance of the real class you can easily retrieve the real class by using the Doctrine Common ClassUtils:

use Doctrine\Common\Util\ClassUtils;

and then you can get the real class through the static getClass method like this:

$proxyOrEntity;

$className = ClassUtils::getClass($proxyOrEntity);

So this means @Benjamin his isEntity function can be written like this:

/**
 * @param EntityManager $em
 * @param string|object $class
 *
 * @return boolean
 */
function isEntity(EntityManager $em, $class)
{
    if(is_object($class)){
        $class = ClassUtils::getClass($class);
    }
    return ! $em->getMetadataFactory()->isTransient($class);
}

Which will give you true/false depending on whether the class is a doctrine entity or not.

One work around would be to test if you can generate a Repository. This is 'bullet proof' in that it will fail if the current schema and mapping does not know about the object class in question.

// Get the entity manager. I don't know how you do it
$em = new Doctrine\ORM\EntityManager();

try {
    $repo = $em->getRepository('YourClassModel');
} catch (Doctrine\Common\Persistence\Mapping\MappingException $e) {
    // NOPE! Not a mapped model
}