Question

I am having a problem with Memcache being unable to set a key. Basically I have my testing page:

$db=new db;
$my_test_cache=$db->query("SELECT `txt` FROM `lang` WHERE `pg`='front' LIMIT 2", 10);

And a db class for caching:

class db {
        public function query($query, $ttl=30, $cache=true, $compr=false) {
            global $memcache;
            if ($cache==true) {
                $res=$memcache->get(hash('md4', $query));
                if ($res!=false) {
                    echo 'this is cached';
                    return $res;
                }
                else {
                    $res=mysql_query($query);
                    $memcache->set(hash('md4', $query), $res, $compr, $ttl);
                    echo 'this is not cached<hr>
                    Query: ',$query,'<br/>
                    Md4: ',hash('md4',$query),'<br/>';
                    var_dump($res);
                    return $res;
                }
            }
            else return mysql_query($query);
            unset($res, $query);
        }
    }

Sadly, this does not set any data to cache, even though all the resources seem to work properly. AKA my page outputs:

• this is not cached Query: SELECT * FROM lang WHERE pg=’front’
  LIMIT 2
• Md4: 34aa4e46a15413f5091dac79c9e86306
• resource(7) of type (mysql result)

Would anyone be so kind as to tip me off on what to do here?

Answer 1

Typo:

        if ($cache=true) {
                  ^--- should be ==

As well, unless memcache is far smarter than I think it is, you’re simply cacheing a query result handle, not the actual query results:

       $memcache->set(hash('md4', $query), $res, $compr, $ttl);
                                           ^^^^

At that point, $res is just a randomish number, NOT the txt field you requested. You have to first FETCH a row from that result in order to retrieve the data:

       $result = mysql_query(...) or die(mysql_error());
       $row = mysql_fetch_assoc($result);
       $txt = $row['txt'];