php - using SimpleXML to parse OAI PMH file

curl, oai, php, simplexml

Solution

To access children with their own namespace, you have to tell `SimpleXMLElement` that you want children not in the default langauge. See `SimpleXMLElement::children`.

The document you linked makes use of multiple namespaces so it's probably a bit confusing if you're new to it.

The following is some example code which extends yours (and simplifies the loading a bit but I think you understand it) to access the children inside the first record element (I break the loop):

$url = 'http://mdc.cbuc.cat/cgi-bin/oai.exe?verb=ListRecords&metadataPrefix=oai_dc&set=afcecemc&from=2011-06-21&until=2011-06-21';

$xmlObj = simplexml_load_file($url);

$xmlNode = $xmlObj->ListRecords;

foreach ($xmlNode->record as $rNode) {
    var_dump($rNode->children());
    var_dump($rNode->metadata->children('oai_dc', 1));
    var_dump($rNode->metadata->children('oai_dc', 1)->dc->children('dc', 1));
    break;
}

This gives the following output which I guess is what you're looking for:

object(SimpleXMLElement)#7 (2) {
  ["header"]=>
  object(SimpleXMLElement)#9 (3) {
    ["identifier"]=>
    string(29) "oai:mdc.cbuc.cat:afcecemc/521"
    ["datestamp"]=>
    string(10) "2011-06-21"
    ["setSpec"]=>
    string(8) "afcecemc"
  }
  ["metadata"]=>
  object(SimpleXMLElement)#10 (0) {
  }
}
object(SimpleXMLElement)#10 (1) {
  ["dc"]=>
  object(SimpleXMLElement)#8 (0) {
  }
}
object(SimpleXMLElement)#7 (12) {
  ["title"]=>
  string(12) "Puig d'Assas"
  ["creator"]=>
  string(26) "Gallardo i Garriga, Antoni"
  ["date"]=>
  string(19) "[Entre 1912 i 1928]"
  ["relation"]=>
  array(2) {
    [0]=>
    string(72) "Paper; gelatina i plata; positiu; blanc i negre; horitzontal; 12 x 17 cm"
    [1]=>
    string(27) "Estudi de la Masia Catalana"
  }
  ["subject"]=>
  string(9) "Muntanyes"
  ["coverage"]=>
  string(32) "Puig d'Assas ; Osona ; Catalunya"
  ["description"]=>
  array(2) {
    [0]=>
    string(2) "Bo"
    [1]=>
    string(163) "Títol atorgat pel catalogador. Informació extreta dels àlbums de l'EMC: Situació: Puig d'Assas. Facilitada per: Antoni Gallardo i Garriga. Facilitada en: 1928."
  }
  ["publisher"]=>
  string(33) "Centre Excursionista de Catalunya"
  ["source"]=>
  string(29) "Memòria Digital de Catalunya"
  ["type"]=>
  string(5) "Image"
  ["rights"]=>
  string(49) "http://creativecommons.org/licenses/by-nc-nd/3.0/"
  ["identifier"]=>
  string(35) "http://mdc.cbuc.cat/u?/afcecemc,521"
}

Problem

I'm trying to parse this file: http://mdc.cbuc.cat/cgi-bin/oai.exe?verb=ListRecords&metadataPrefix=oai_dc&set=afcecemc&from=2011-06-21&until=2011-06-21 using SimpleXML. I can get all elements but those wich are inside the tag. It says that the tag is empty. Here is my code. ``` function getXMLfile($URL) { $chDyn = curl_init(); curl_setopt ($chDyn, CURLOPT_URL, $URL); curl_setopt($chDyn, CURLOPT_RETURNTRANSFER, 1); $xml = curl_exec($chDyn); curl_close($chDyn); try { $xmlObj = new SimpleXMLElement($xml); } catch (Exception $e) { echo $e; } return $xmlObj; } $cdmURL = "http://mdc.cbuc.cat/cgi-bin/oai.exe?verb=ListRecords&metadataPrefix=oai_dc&set=afcecemc"; $xmlObj = getXMLfile($cdmURL); $xmlNode = $xmlObj->ListRecords; foreach ($xmlNode->record as $rNode) { var_dump($rNode->children()); } ``` But the output is this one: ``` [...] ["metadata"]=> object(SimpleXMLElement)#8 (0) { } ``` This element is not empty! I know that the solution is somehow related with using "namespaces" but I can't figure out how to make it works. Any help it will be appreciated! Thanks.

Original source