PHP and MySQL Web Development 4th Ed-tqw-_darksiderg

848 Chapter 33 Connecting to Web Services with XML and SOAP
Listing 33.12
Continued
}
// is cached data missing or > 1 hour old?
if(!file_exists($filename) ||
((mktime() - filemtime($filename)) > 60*60)) {
return false;
}
$data = file_get_contents($filename);
return unserialize($data);
}
// add Amazon data to the cache
function cache($type, $parameters, $data) {
if($type == 'browse') {
$filename = CACHE.'/browse.'.$parameters['browsenode'].'.'
.$parameters['page'].'.'.$parameters['mode'].'.dat';
}
if($type == 'search') {
$filename = CACHE.'/search.'.$parameters['search'].'.'
.$parameters['page'].'.'.$parameters['mode'].'.dat';
}
if($type == 'asin') {
$filename = CACHE.'/asin.'.$parameters['asin'].'.'
.$parameters['mode'].'.dat';
}
$data = serialize($data);
$fp = fopen($filename, 'wb');
if(!$fp || (fwrite($fp, $data)==-1)) {
echo ('Error, could not store cache file');
}
fclose($fp);
Looking through this code, you can see that cache files are stored under a filename that
consists of the type of query followed by the query parameters.The cache() function
stores results by serializing them, and the cached() function deserializes them.The
cached() function will also overwrite any data more than an hour old, as per the terms
and conditions.
The function serialize() turns stored program data into a string that can be stored.
In this case, you create a storable representation of an AmazonResultSet object. Calling
unserialize() does the opposite, turning the stored version back into a data structure