Question

Consider the following function prototype for caching object from cached RSS(XML) feed:

function cacheObject($xml,$name,$age = 3600)
  { 
    // directory in which to store cached files
    $cacheDir = "cache/";
    // cache filename
    $filename = $cacheDir.$name;
    // default to fetch the file
    $cache = true;
    // but if the file exists, don't fetch if it is recent enough
    if (file_exists($filename))
    {
      $cache = (filemtime($filename) < (time()-$age));
    }
    // fetch the file if required
    if ($cache)
    {
      $item = $xml->channel->item;
      file_put_contents($filename,serialize($item));
      // update timestamp to now
      touch($filename);
    }
    // return the cache filename
    return unserialize(file_get_contents($filename));
  }   

The function calls are as follows:

$urlD = "http://somerss.php";
    $xmlD = simplexml_load_file(cacheFetch($urlD,'cachedfeedD.xml',3600));
    $itemD = '';
    if($xmlD === FALSE)
        {$itemD = '';}
    else
        {$itemD = cacheObject($xmlD,'cacheobjectD',3600);}
 $urlM = "somerss2.php";
    $xmlM = simplexml_load_file(cacheFetch($urlM,'cachedfeedM.xml',3600));
    $itemM = '';
    if($xmlM ===  FALSE) 
        {$itemM = '';}
    else
        {$itemM = cacheObject($xmlM,'cacheobjectM',3600);}

I get the following error:

    Fatal error: Uncaught exception 'Exception' 
with message 'Serialization of 'SimpleXMLElement' is not allowed' in C:\xampp\htdocs\sitefinal\cacheObject.php:20 Stack trace: #0 C:\xampp\htdocs\sitefinal\cacheObject.php(20): serialize(Object(SimpleXMLElement)) 

Any help making this program to work is greatly appreciated.

Answer 1

Probably, the SimpleXMLElement class, like many built-in PHP objects, cannot be serialized.

Instead, you could call the class method asXML (which returns a valid XML string if you pass no parameters) and serialize this. You can then recreate the SimpleXMLElement class by calling simplexml_load_string() on this string.