/** * Serialise an EasyRdf\Graph into a JSON-LD document. * * @param Graph $graph An EasyRdf\Graph object. * @param string $format The name of the format to convert to. * @param array $options * * @return string The RDF in the new desired format. * @throws Exception */ public function serialise(Graph $graph, $format, array $options = array()) { parent::checkSerialiseParams($format); if ($format != 'jsonld') { throw new Exception(__CLASS__ . ' does not support: ' . $format); } $ld_graph = new LD\Graph(); $nodes = array(); // cache for id-to-node association foreach ($graph->toRdfPhp() as $resource => $properties) { if (array_key_exists($resource, $nodes)) { $node = $nodes[$resource]; } else { $node = $ld_graph->createNode($resource); $nodes[$resource] = $node; } foreach ($properties as $property => $values) { foreach ($values as $value) { if ($value['type'] == 'bnode' or $value['type'] == 'uri') { if (array_key_exists($value['value'], $nodes)) { $_value = $nodes[$value['value']]; } else { $_value = $ld_graph->createNode($value['value']); $nodes[$value['value']] = $_value; } } elseif ($value['type'] == 'literal') { if (isset($value['lang'])) { $_value = new LD\LanguageTaggedString($value['value'], $value['lang']); } elseif (isset($value['datatype'])) { $_value = new LD\TypedValue($value['value'], $value['datatype']); } else { $_value = $value['value']; } } else { throw new Exception("Unable to serialise object to JSON-LD: " . $value['type']); } if ($property == "http://www.w3.org/1999/02/22-rdf-syntax-ns#type") { $node->addType($_value); } else { $node->addPropertyValue($property, $_value); } } } } // OPTIONS $use_native_types = !(isset($options['expand_native_types']) and $options['expand_native_types'] == true); $should_compact = (isset($options['compact']) and $options['compact'] == true); $should_frame = isset($options['frame']); // expanded form $data = $ld_graph->toJsonLd($use_native_types); if ($should_frame) { $data = LD\JsonLD::frame($data, $options['frame'], $options); } if ($should_compact) { // compact form $compact_context = isset($options['context']) ? $options['context'] : null; $compact_options = array('useNativeTypes' => $use_native_types, 'base' => $graph->getUri()); $data = LD\JsonLD::compact($data, $compact_context, $compact_options); } return LD\JsonLD::toString($data); }