$element['namespace'] is sometimes and array not a single value.

As the title says, $element['namespace'] is sometimes and array not a single value. Which means when you array_merge on line 198 and then implode on line 201 the result is :

xmlns:dc="http://purl.org/dc/elements/1.1/" Array

This is due to the code on line 115-> 121

      foreach ($extra as $element) {
        if ($element['namespace']) {
          $namespaces[] = $element['namespace'];
        }
      }

Should be (assuming it may be an array or single value) :

      foreach ($extra as $element) {
        if(is_array($element['namespace'])) {
          foreach ($element['namespace'] as $elements_namespace) {
            $namespaces[] = $elements_namespace;
          }
        } 
        else if ($element['namespace']) {
          $namespaces[] = $element['namespace'];
        }
      }

a_c_m