为什么我得到这个PHP警告？

为foreach()提供的参数无效

这是我的代码:

// look for text file for this keyword
if (empty($site["textdirectory"])) {
    $site["textdirectory"] = "text";
}
if (file_exists(ROOT_DIR.$site["textdirectory"].'/'.urlencode($q).'.txt')) {
    $keywordtext = 
     file_get_contents(ROOT_DIR.$site["textdirectory"].'/'.urlencode($q).'.txt');
}
else {
    $keywordtext = null;
}

$keywordsXML = getEbayKeywords($q);

foreach($keywordsXML->PopularSearchResult as $item) {
    $topicsString = $item->AlternativeSearches;
   $relatedString = $item->RelatedSearches;
   if (!empty($topicsString)) {
        $topics =  split(";",$topicsString);
    }
    if (!empty($relatedString)) {
        $related = split(";",$relatedString);
    }

}

$node = array();
$node['keywords'] = $q;

2

$xml = ebay_rss($node);

$ebayItems = array();
$totalItems = count($xml->channel->item);

$totalPages = $totalItems …