SimplePie_Misc::is_isegment_nz_nc PHP Method

    function is_isegment_nz_nc($string)
    {
        return (bool) preg_match('/^([A-Za-z0-9\\-._~\\x{A0}-\\x{D7FF}\\x{F900}-\\x{FDCF}\\x{FDF0}-\\x{FFEF}\\x{10000}-\\x{1FFFD}\\x{20000}-\\x{2FFFD}\\x{30000}-\\x{3FFFD}\\x{40000}-\\x{4FFFD}\\x{50000}-\\x{5FFFD}\\x{60000}-\\x{6FFFD}\\x{70000}-\\x{7FFFD}\\x{80000}-\\x{8FFFD}\\x{90000}-\\x{9FFFD}\\x{A0000}-\\x{AFFFD}\\x{B0000}-\\x{BFFFD}\\x{C0000}-\\x{CFFFD}\\x{D0000}-\\x{DFFFD}\\x{E1000}-\\x{EFFFD}!$&\'()*+,;=@]|(%[0-9ABCDEF]{2}))+$/u', $string);
    }

 public function get_links($rel = 'alternate')
 {
     if (!isset($this->data['links'])) {
         $this->data['links'] = array();
         foreach ((array) $this->get_item_tags(SIMPLEPIE_NAMESPACE_ATOM_10, 'link') as $link) {
             if (isset($link['attribs']['']['href'])) {
                 $link_rel = isset($link['attribs']['']['rel']) ? $link['attribs']['']['rel'] : 'alternate';
                 $this->data['links'][$link_rel][] = $this->sanitize($link['attribs']['']['href'], SIMPLEPIE_CONSTRUCT_IRI, $this->get_base($link));
             }
         }
         foreach ((array) $this->get_item_tags(SIMPLEPIE_NAMESPACE_ATOM_03, 'link') as $link) {
             if (isset($link['attribs']['']['href'])) {
                 $link_rel = isset($link['attribs']['']['rel']) ? $link['attribs']['']['rel'] : 'alternate';
                 $this->data['links'][$link_rel][] = $this->sanitize($link['attribs']['']['href'], SIMPLEPIE_CONSTRUCT_IRI, $this->get_base($link));
             }
         }
         if ($links = $this->get_item_tags(SIMPLEPIE_NAMESPACE_RSS_10, 'link')) {
             $this->data['links']['alternate'][] = $this->sanitize($links[0]['data'], SIMPLEPIE_CONSTRUCT_IRI, $this->get_base($links[0]));
         }
         if ($links = $this->get_item_tags(SIMPLEPIE_NAMESPACE_RSS_090, 'link')) {
             $this->data['links']['alternate'][] = $this->sanitize($links[0]['data'], SIMPLEPIE_CONSTRUCT_IRI, $this->get_base($links[0]));
         }
         if ($links = $this->get_item_tags(SIMPLEPIE_NAMESPACE_RSS_20, 'link')) {
             $this->data['links']['alternate'][] = $this->sanitize($links[0]['data'], SIMPLEPIE_CONSTRUCT_IRI, $this->get_base($links[0]));
         }
         if ($links = $this->get_item_tags(SIMPLEPIE_NAMESPACE_RSS_20, 'guid')) {
             if (!isset($links[0]['attribs']['']['isPermaLink']) || strtolower(trim($links[0]['attribs']['']['isPermaLink'])) === 'true') {
                 $this->data['links']['alternate'][] = $this->sanitize($links[0]['data'], SIMPLEPIE_CONSTRUCT_IRI, $this->get_base($links[0]));
             }
         }
         $keys = array_keys($this->data['links']);
         foreach ($keys as $key) {
             if (SimplePie_Misc::is_isegment_nz_nc($key)) {
                 if (isset($this->data['links'][SIMPLEPIE_IANA_LINK_RELATIONS_REGISTRY . $key])) {
                     $this->data['links'][SIMPLEPIE_IANA_LINK_RELATIONS_REGISTRY . $key] = array_merge($this->data['links'][$key], $this->data['links'][SIMPLEPIE_IANA_LINK_RELATIONS_REGISTRY . $key]);
                     $this->data['links'][$key] =& $this->data['links'][SIMPLEPIE_IANA_LINK_RELATIONS_REGISTRY . $key];
                 } else {
                     $this->data['links'][SIMPLEPIE_IANA_LINK_RELATIONS_REGISTRY . $key] =& $this->data['links'][$key];
                 }
             } elseif (substr($key, 0, 41) === SIMPLEPIE_IANA_LINK_RELATIONS_REGISTRY) {
                 $this->data['links'][substr($key, 41)] =& $this->data['links'][$key];
             }
             $this->data['links'][$key] = array_unique($this->data['links'][$key]);
         }
     }
     if (isset($this->data['links'][$rel])) {
         return $this->data['links'][$rel];
     } else {
         return null;
     }
 }