GraphQL\Utils::filter PHP Method

    public static function filter($traversable, callable $predicate)
    {
        self::invariant(is_array($traversable) || $traversable instanceof \Traversable, __METHOD__ . ' expects array or Traversable');
        $result = [];
        $assoc = false;
        foreach ($traversable as $key => $value) {
            if (!$assoc && !is_int($key)) {
                $assoc = true;
            }
            if ($predicate($value, $key)) {
                $result[$key] = $value;
            }
        }
        return $assoc ? $result : array_values($result);
    }

 /**
  * Return implementations of `type` that include `fieldName` as a valid field.
  *
  * @param Schema $schema
  * @param AbstractType $type
  * @param $fieldName
  * @return array
  */
 static function getImplementationsIncludingField(Schema $schema, AbstractType $type, $fieldName)
 {
     $types = $schema->getPossibleTypes($type);
     $types = Utils::filter($types, function ($t) use($fieldName) {
         return isset($t->getFields()[$fieldName]);
     });
     $types = Utils::map($types, function ($t) {
         return $t->name;
     });
     sort($types);
     return $types;
 }