isset vs try/catch on namespaces - php

Question

I'm parsing RSS feeds and have a (sub)function that looks like this:
function nSpace($nSp, $type, $i){
$namespaces = $i->getNameSpaces(true);
$exp = explode(':', $nSp);
try{
$nameSp = $i->children($namespaces[$exp[0]]);
$item[$type] = (string)$nameSp->$exp[1];
return $item[$type];
}
catch (Exception $e) { }
}
I'm trying to retrieve the namespace value, and will pass common RSS feed namespaces like "dc:date" or "content:encoded" for example as $nSp. The function works fine should the namespace exist in the XML, however the try{} is producing an 'Undefined Index' error in the first line when it doesn't.
Personally I'd rather run an isset($i->children($namespaces[$exp[0]])){} check instead of the try/catch, as I'm more familiar with that workflow, however this doesn't work (get a 'Can't use return value' error).
Few questions:
Shouldn't the try{} not produce error messages?
Is try/catch the best way?
Is there a way to do it with an if() instead?
Thanks.
Update:
Here is the (abreviated) call/usage for this function:
$rawFeed = file_get_contents($url);
try { $rss = new SimpleXMLElement($rawFeed); } catch (Exception $e) { }
foreach ($rss->channel->item as $i) {
$item['link'] = isset($i->link) ? (string)$i->link : nSpace('dc:link', 'link', $i);
$item['dateRaw'] = isset($i->pubDate) ? (string)$i->pubDate : nSpace('dc:date', 'date', $i);
// etc...
}