Neo4j - Graphaware reco4php - Problem with namespaces

Question

I'm trying to run the demo from Neo4j - reco4php page at This Link I followed every steps very carefully but i'm getting a strange error at the end.

let me explain in more details :

This is the code I'm trying to run :

require 'vendor/autoload.php';

use GraphAware\Common\Cypher\Statement;
use GraphAware\Common\Type\Node;
use GraphAware\Reco4PHP\Context\Context;
use GraphAware\Reco4PHP\Engine\SingleDiscoveryEngine;

class RatedByOthers extends SingleDiscoveryEngine
{
public function discoveryQuery(Node $input, Context $context)
{
    $query = 'MATCH (input:User) WHERE id(input) = {id}
    MATCH (input)-[:RATED]->(m)<-[:RATED]-(o)
    WITH distinct o
    MATCH (o)-[:RATED]->(reco)
    RETURN distinct reco LIMIT 500';

    return Statement::create($query, ['id' => $input->identity()]);
}

public function name()
{
    return "rated_by_others";
}
}

This above code extends the class "SingleDiscoveryEngine" :

declare (strict_types = 1);

namespace GraphAware\Reco4PHP\Engine;

use GraphAware\Common\Result\Record;
use GraphAware\Common\Result\ResultCollection;
use GraphAware\Common\Type\Node;
use GraphAware\Reco4PHP\Context\Context;
use GraphAware\Reco4PHP\Result\Recommendations;
use GraphAware\Reco4PHP\Result\SingleScore;

abstract class SingleDiscoveryEngine implements DiscoveryEngine
{
private static $DEFAULT_RECO_NAME = 'reco';
private static $DEFAULT_SCORE_NAME = 'score';
private static $DEFAULT_REASON_NAME = 'reason';


public function buildScore(Node $input, Node $item, Record $record, Context 
$context) : SingleScore
{
    $score = $record->hasValue($this->scoreResultName()) ? $record- >value($this->scoreResultName()) : $this->defaultScore();
    $reason = $record->hasValue($this->reasonResultName()) ? $record- >value($this->reasonResultName()) : null;

    return new SingleScore($score, $reason);
}


final public function produceRecommendations(Node $input, ResultCollection 
$resultCollection, Context $context) : Recommendations
{
    $result = $resultCollection->get($this->name());
    $recommendations = new Recommendations($context);

    foreach ($result->records() as $record) {
        if ($record->hasValue($this->recoResultName())) {
            $recommendations->add($record->get($this->recoResultName()), $this->name(), $this->buildScore($input, $record->get($this->recoResultName()), 
$record, $context));
        }
    }

    return $recommendations;
}

/**
 * {@inheritdoc}
 */
public function recoResultName() : string
{
    return self::$DEFAULT_RECO_NAME;
}

/**
 * {@inheritdoc}
 */
public function scoreResultName() : string
{
    return self::$DEFAULT_SCORE_NAME;
}

/**
 * {@inheritdoc}
 */
public function reasonResultName() : string
{
    return self::$DEFAULT_REASON_NAME;
}

/**
 * {@inheritdoc}
 */
public function defaultScore() : float
{
    return 1.0;
}
}

and the above class is also implements the following class :

namespace GraphAware\Reco4PHP\Engine;

use GraphAware\Common\Cypher\StatementInterface;
use GraphAware\Common\Result\Record;
use GraphAware\Common\Type\Node;
use GraphAware\Common\Result\ResultCollection;
use GraphAware\Reco4PHP\Context\Context;
use GraphAware\Reco4PHP\Result\Recommendations;
use GraphAware\Reco4PHP\Result\SingleScore;

interface DiscoveryEngine
{
/**
 * @return string The name of the discovery engine
 */
public function name() : string;

/**
 * The statement to be executed for finding items to be recommended.
 *
 * @param Node    $input
 * @param Context $context
 *
 * @return \GraphAware\Common\Cypher\Statement
 */
public function discoveryQuery(Node $input, Context $context) : StatementInterface;

/**
 * Returns the score produced by the recommended item.
 *
 * @param Node    $input
 * @param Node    $item
 * @param Record  $record
 * @param Context $context
 *
 * @return \GraphAware\Reco4PHP\Result\SingleScore A single score produced for the recommended item
 */
public function buildScore(Node $input, Node $item, Record $record, Context $context) : SingleScore;

/**
 * Returns a collection of Recommendation object produced by this discovery engine.
 *
 * @param Node             $input
 * @param ResultCollection $resultCollection
 * @param Context          $context
 *
 * @return Recommendations
 */
public function produceRecommendations(Node $input, ResultCollection $resultCollection, Context $context) : Recommendations;

/**
 * @return string The column identifier of the row result representing the recommended item (node)
 */
public function recoResultName() : string;

/**
 * @return string The column identifier of the row result representing the score to be used, note that this
 *                is not mandatory to have a score in the result. If empty, the score will be the float value returned by
 *                <code>defaultScore()</code> or the score logic if the concrete class override the <code>buildScore</code>
 *                method.
 */
public function scoreResultName() : string;

/**
 * @return float The default score to be given to the discovered recommended item
 */
public function defaultScore() : float;
}

And when I run the code I'm getting the following error :

Fatal error: Declaration of RatedByOthers::name() must be compatible with GraphAware\\Reco4PHP\\Engine\\DiscoveryEngine::name(): string in /Applications/XAMPP/xamppfiles/htdocs/reco/index.php on line 9

I checked the code for hours and I think it should works fine and I have no idea where the problem comes from.

Answer 1

I found the answer myself.

The problem solved by declaring the type of return right after function starts :

public function discoveryQuery(Node $input, Context $context) : GraphAware\Common\Cypher\StatementInterface   {
$query = 'MATCH (input:User) WHERE id(input) = {id}
MATCH (input)-[:RATED]->(m)<-[:RATED]-(o)
WITH distinct o
MATCH (o)-[:RATED]->(reco)
RETURN distinct reco LIMIT 500';

return Statement::create($query, ['id' => $input->identity()]);
}

public function name() : string 
{
return "rated_by_others";
}

hope it can help someone else in the future.