PHP caching function code_PHP tutorial

**
* @Description: File cache output
* @parameter : $cachefile => cache file (absolute path)
* @Parameter: $pertime => Cache output interval
* @Parameter: $sql => sql statement
* @Parameter: $templatefile => Template file name (absolute path)
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**/
function __cache($cachefile,$pertime,$sql,$templatefile) {
global $db;
if(time() - @filemtime($cachefile) >= $pertime) {
$query = $db->query($sql);
while($r =$db->fetch($query)) {
$cachelist[] = $r;
}
include $templatefile.'.php';
$cacheserialize = serialize($cachelist );
file_put_contents($cachefile,$cacheserialize);
}else{
$cachelist = unserialize(file_get_contents($cachefile));
include $templatefile.'.php';
}
}