问PHP7致命错误:声明.必须与

EN

Fatal error: Declaration of GraphAware\Reco4PHP\Demo\Github\RecommendationEngine::discoveryEngines() must be compatible with GraphAware\Reco4PHP\Engine\RecommendationEngine::discoveryEngines(): array in /var/www/html/reco-fresh/_demo/github/RecommendationEngine.php on line 5

namespace GraphAware\Reco4PHP\Demo\Github;

class RecommendationEngine extends \GraphAware\Reco4PHP\Engine\BaseRecommendationEngine
{
    public function discoveryEngines()
    {
        return array(
            new FollowedByFollowers(),
            new SameContribution()
        );
    }    
}

namespace GraphAware\Reco4PHP\Engine;

use GraphAware\Common\Type\Node;
use GraphAware\Reco4PHP\Context\Context;
use GraphAware\Reco4PHP\Persistence\DatabaseService;

interface RecommendationEngine
{
    public function name() : string;

    public function discoveryEngines() : array;
}

namespace GraphAware\Reco4PHP\Engine;

use GraphAware\Reco4PHP\Context\Context;
use GraphAware\Reco4PHP\Executor\RecommendationExecutor;
use GraphAware\Reco4PHP\Filter\BlackListBuilder;
use GraphAware\Reco4PHP\Filter\Filter;
use GraphAware\Reco4PHP\Persistence\DatabaseService;
use GraphAware\Common\Type\Node;
use GraphAware\Reco4PHP\Post\PostProcessor;
use GraphAware\Reco4PHP\Result\Recommendations;
use Psr\Log\LoggerInterface;

abstract class BaseRecommendationEngine implements RecommendationEngine
{
    private $databaseService;

    private $recommendationExecutor;

    public function discoveryEngines() : array
    {
        return array();
    }
}