php缓存机制的相关代码！一段来自uchome的代码，可以学习！

function.eventclass_cache.php

<?php
#活动类别函数
function eventclass_cache(){
    global $_SGLOBAL;

    $_SGLOBAL['eventclass'] = array();
	#同时写入全局
	$query = $_SGLOBAL['db']->query("SELECT * FROM " . tname("eventclass") . " ORDER BY displayorder");
	while($value = $_SGLOBAL['db']->fetch_array($query)){
		if($value['poster']) {
			$value['poster'] = "data/event/".$value['classid'].".jpg";
		} else {
			$value['poster'] = "image/event/default.jpg";
		}
	    $_SGLOBAL['eventclass'][$value['classid']] = $value;
	}
	cache_write('eventclass', "_SGLOBAL['eventclass']", $_SGLOBAL['eventclass']);
}
#写入缓存
function cache_write($name, $var, $values) {
    #指定文件path
    $cachefile = S_ROOT.'./data/data_'.$name.'.php';
	$cachetext = "<?php\r\n".
		"if(!defined('IN_UCHOME')) exit('Access Denied');\r\n".
		'$'.$var.'='.arrayeval($values).
		"\r\n?>";
	if(!swritefile($cachefile, $cachetext)) {
		exit("File: $cachefile write error.");
	}
}
#写文件
function swritefile($filename, $writetext, $openmod='w') {
    if(@$fp = fopen($filename, $openmod)) {
		flock($fp, 2);
		fwrite($fp, $writetext);
		fclose($fp);
		return true;
	} else {
		runlog('error', "File: $filename write error.");
		return false;
	}
}

?>