simplexml_load_string and simplexml_load_file are buggy and don't work well on XML with a complex markup. I tried both functions to parse some VALID XML SOAP responses and could not even get an error message. I had to use DOMDocument instead (worked like a charm).

Here is how we suppose to check simplexml for errors (if you are lucky to see errors, not just "false" returned from function)

libxml_use_internal_errors(true);
$xml=simplexml_load_string($myXMLData); //or simplexml_load_file

foreach( libxml_get_errors() as $error ) {

    print_r($error);

}

You can simply iterate the SimpleXMLElement objects by accessing the children with -> operator:

$xml = <<<'XML'
<info>
    <form tableid="1">
        <town_id>
            <option value="5102">Moscow</option>
            <option value="2587">London</option>
            <option value="717">Madrid</option>
            <option value="2513">Paris</option>
            <option value="5071">Berlin</option>
        </town_id>
        <town_id>
            <option value="9343">XTown</option>
        </town_id>
    </form>
</info>
XML;

$items = simplexml_load_string($xml);

foreach ($items as $form) {
    foreach ($form->town_id as $town) {
        foreach ($town->option as $option) {
            $attr = $option->attributes();
            printf("#%d - %s\n", $attr['value'], $option);
        }
    }
}

Output

#5102 - Moscow
#2587 - London
#717 - Madrid
#2513 - Paris
#5071 - Berlin
#9343 - XTown

XPath

Alternatively, use xpath method:

$options = $items->xpath('form/town_id/option');
foreach ($options as $option) {
  $attr = $option->attributes();
  printf("#%d - %s\n", $attr['value'], $option);
}

In this example I used an XPath expression relative to $items (root element, in particular). Adjust the XPath according to your needs. For example, you can fetch all options in the document with //option. Or you might even want to iterate all elements under form having option children:

$containers = $items->xpath('form/*[option]');
foreach ($containers as $c) {
  switch ($c->getName()) {
    case 'town_id':    $label = 'Towns';     break;
    case 'country_id': $label = 'Countries'; break;
    default:
      // Skipping unknown element name
      continue;
  }

  printf("\n%s\n======\n", $label);
  foreach ($c->option as $option) {
    $attr = $option->attributes();
    printf("#%d - %s\n", $attr['value'], $option);
  }
}

Sample Output

Towns
======
#5102 - Moscow
#2587 - London
#717 - Madrid
#2513 - Paris
#5071 - Berlin

Towns
======
#9343 - XTown

Countries
======
#3456 - Russia
#4566 - China