I know this code is incorrect, but it's a basis of what I am trying to achieve.

I am parsing an xml feed via PHP and running a foreach loop to get a value from a specific key.

Here is the snippet I am using:

$feed = file_get_contents("https://www.feedurl.com/xml"); // Feed URL
$xml = new SimpleXmlElement($feed);

$output = array();
foreach($xml->entry as $entry){
  $attributes = $entry->id->attributes(URI_RSS);
  $im = $entry->children(URI_RSS);                                    

  // Get item's ID
  $id = $entry->id;
  $attr = $id->attributes('im', TRUE);

  $output[] = $attr['id'];

$testarray = "'" . implode("', '", $output) . "'"; // Place the 'output' from the foreach into this formation: 'xxx','xxx','xxx',etc    
$lastarray = array($testarray);

$args = array(
  'post_type' => $post_type,
  'post__in'      => $lastarray

$wp_query = new WP_Query( $args );

When I echo '$testarray' it displays correctly in the way I had set it up: 'xxx','xxx','xxx',etc

However, trying to place '$testarray' as an array for 'post__in' doesn't work. I know for sure my code isn't set correctly and am not sure how I would do it.

The 'post__in' would be paginated, loading via a infinite loop.

Thanks! Joe.

2 Answers 2


Looking at your code - $lastarray will not be an array of ID's (as you might be expecting), but an array with a single element containing a string of comma separated IDs.

$output is already an array of the $attr['id'] - try commenting (add // to the start) to the lines starting with $testarray and $lastarray and replacing 'post__in' => $lastarray with 'post__in' => $output

See if that helps.

Edit: to clarify - post__in expects an array (rather than 'id','id','id' string) - see here


  • Thanks for the tip, using 'post__in' => $output, I get the error: Fatal error: Uncaught exception 'Exception' with message 'Serialization of 'SimpleXMLElement' is not allowed' When I echo $output; - It prints the word Array instead of the values for $attr['id']
    – Roc
    Commented Mar 12, 2014 at 15:02
  • echo $output[1]; does print out the individual values however, so I do believe this is the right track.
    – Roc
    Commented Mar 12, 2014 at 15:09
  • You can use var_dump or print_r to view an array; var_dump($output) and print_r($output) should show you what you've got in the array. Commented Mar 12, 2014 at 15:16
  • You need to cast the variables as strings (I think, not worked much with SimpleXML). Try adding (string) before the variables are worked out - for example; $attributes = (string) $entry->id->attributes(URI_RSS); Commented Mar 12, 2014 at 15:21

Update to know that I was able to accomplish this by this snippet below:

For reference:

$jsonfeed = file_get_contents('http://www.jsonfeed.com');
$results = json_decode($top100, true);

foreach($results['feed']['entry'] as $post){ // This is custom for my json
  $post_ids[] = $entry['id']['attributes']['second_id'];

var_dump($post_ids); // dump array

$args = array(
  'post_type' => $post_type,
  'post__in'  => $post_ids,
  'ignore_sticky_posts' => 1,

$wp_query = new WP_Query( $args );

if (have_posts()) :
   usort($wp_query->posts, function($a, $b) use ($post_ids) { // Lists loop in order of the array -> http://pastebin.com/3vwiDSfb
      return array_search($a->ID, $post_ids) - array_search($b->ID, $post_ids);
   while(have_posts()) : the_post();

Thanks for all that helped.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.