PKPString::trimPunctuation PHP Method

    static function trimPunctuation($string)
    {
        return trim($string, ' ,.;:!?&()[]\\/');
    }

 /**
  * @copydoc Filter::process()
  * @param $isbn string
  * @return MetadataDescription a looked up citation description
  *  or null if the filter fails
  */
 function &process($isbn)
 {
     $nullVar = null;
     // Instantiate the web service request
     $lookupParams = array('access_key' => $this->getApiKey(), 'index1' => 'isbn', 'results' => 'details,authors', 'value1' => $isbn);
     // Call the web service
     if (is_null($resultDOM =& $this->callWebService(ISBNDB_WEBSERVICE_URL, $lookupParams))) {
         return $nullVar;
     }
     // Transform and pre-process the web service result
     if (is_null($metadata =& $this->transformWebServiceResults($resultDOM, dirname(__FILE__) . DIRECTORY_SEPARATOR . 'isbndb.xsl'))) {
         return $nullVar;
     }
     // Extract place and publisher from the combined entry.
     $metadata['publisher-loc'] = PKPString::trimPunctuation(PKPString::regexp_replace('/^(.+):.*/', '\\1', $metadata['place-publisher']));
     $metadata['publisher-name'] = PKPString::trimPunctuation(PKPString::regexp_replace('/.*:([^,]+),?.*/', '\\1', $metadata['place-publisher']));
     unset($metadata['place-publisher']);
     // Reformat the publication date
     $metadata['date'] = PKPString::regexp_replace('/^[^\\d{4}]+(\\d{4}).*/', '\\1', $metadata['date']);
     // Clean non-numerics from ISBN
     $metadata['isbn'] = PKPString::regexp_replace('/[^\\dX]*/', '', $isbn);
     // Set the publicationType
     $metadata['[@publication-type]'] = NLM30_PUBLICATION_TYPE_BOOK;
     return $this->getNlm30CitationDescriptionFromMetadataArray($metadata);
 }