function parseContextLinkHeaders(array $values, IRI $baseIri)
{
// Separate multiple links contained in a single header value
for ($i = 0, $total = count($values); $i < $total; $i++) {
if (strpos($values[$i], ',') !== false) {
foreach (preg_split('/,(?=([^"]*"[^"]*")*[^"]*$)/', $values[$i]) as $v) {
$values[] = trim($v);
}
unset($values[$i]);
}
}
$contexts = $matches = array();
$trimWhitespaceCallback = function ($str) {
return trim($str, "\"' \n\t");
};
// Split the header in key-value pairs
foreach ($values as $val) {
$part = array();
foreach (preg_split('/;(?=([^"]*"[^"]*")*[^"]*$)/', $val) as $kvp) {
preg_match_all('/<[^>]+>|[^=]+/', $kvp, $matches);
$pieces = array_map($trimWhitespaceCallback, $matches[0]);
$part[$pieces[0]] = isset($pieces[1]) ? $pieces[1] : '';
}
if (isset($part['rel']) && in_array('http://www.w3.org/ns/json-ld#context', explode(' ', $part['rel']))) {
$contexts[] = (string) $baseIri->resolve(trim(key($part), '<> '));
}
}
return array_values(array_unique($contexts));
}
/**
* Converts a JSON-LD element to a RDF Quad object
*
* @param Object $element The element to be converted.
*
* @return IRI|TypedValue|LanguageTagged|null The converted element to be used as Quad object.
*/
private function elementToRdf(Object $element)
{
if (property_exists($element, '@value')) {
return Value::fromJsonLd($element);
}
$iri = new IRI($element->{'@id'});
return $iri->isAbsolute() ? $iri : null;
}