PHP开发缓存 vs. 数据库缓存：哪个更适合你的网站？

<?php
//启用缓存
$cache = new Memcache();
$cache->connect('localhost', 11211) or die ("Could not connect memcache");
 
$key = 'article_1';
$result = $cache->get($key);
if(!$result) {
    //如果缓存中没有该值，就从数据库中取出
    $result = Mysql_query("SELECT * FROM article WHERE id=1");
    $result = mysql_fetch_assoc($result);
    //取得数据存入缓存，并设立过期时间(设为10秒钟)
    $cache->set($key, $result, MEMCACHE_COMPRESSED, 10);
}
echo $result['title'];
?>

<?php
//启用缓存
$cache = new Memcache();
$cache->connect('localhost', 11211) or die ("Could not connect memcache");
 
$key = md5($_SERVER['REQUEST_URI']);
$result = $cache->get($key);
if(!$result) {
    //如果缓存中没有该值，就查询数据库，
    $result = mysql_query("SELECT * FROM news ORDER BY id DESC LIMIT 5");
    while($row = mysql_fetch_assoc($result)) {
        $news_list[] = $row;
    }
    //取得的数据存入缓存，并设立过期时间(设为1分钟)
    $cache->set($key, $news_list, MEMCACHE_COMPRESSED, 60);
}
//输出缓存中的数据
foreach($news_list as $news){
echo "<li><a href='{$news['url']}'>{$news['title']}</a></li>";
}
?>

//使用Memcached作为缓存客户端
//启用缓存
$cache = new Memcache();
$cache->connect('localhost', 11211) or die ("Could not connect memcache");
 
$key = md5($_SERVER['REQUEST_URI']);
$cache_result = $cache->get($key);
if($cache_result){
    $result = $cache_result;
}else{
    //执行SQL查询操作
    $result = mysql_query("SELECT * FROM users WHERE name='john'");
    //将查询结果存入缓存，并设立过期时间(设为1小时)
    $cache->set($key, $result, MEMCACHE_COMPRESSED, 3600);
}
//输出查询结果
while($row = mysql_fetch_assoc($result)){
    echo "<p>{$row['id']}: {$row['name']}</p>";
}

//使用Redis作为缓存客户端
//启用缓存
$redis = new Redis();
$redis->connect('localhost', 6379);
 
$key = md5($_SERVER['REQUEST_URI']);
$cache_result = $redis->get($key);
if($cache_result){
    $result = JSON_decode($cache_result, true);
}else{
    //执行SQL查询操作
    $result = mysql_query("SELECT * FROM Goods WHERE id=1");
    while($row = mysql_fetch_assoc($result)){
        $goods_info = $row;
    }
    //将查询结果存入缓存，并设立过期时间(设为5分钟)
    $redis->setex($key, 300, json_encode($goods_info));
}
//输出查询结果
echo "<p>{$goods_info['name']}</p>";
echo "<p>{$goods_info['price']}</p>";