Memcache->get return different array

Question

i made this function: /* MEMCACHE */

function cache_query($sql,$nombre,$tiempo = -1){
    $cache = new Memcache();
    $cache->pconnect('localhost',11211);
    $query_cacheada = $cache->get($nombre);
    if ( $query_cacheada  === false ) {
             /* key not in memcache, perfom query, cache it and return */
         $res = mysql_query($sql);
         $cache->set($nombre,$res, 0, 60*60*24);  
         return $res; /* this looks good */
    }else{
             /* key in memcache, just return cached  */
         return $query_cacheada;  /* this doesnt return right elements */
    }
}

wich i am using so:

class text{

    protected $id;
    protected $key;
    protected $language;
    protected $text;

    function __construct($clave,$lan){
       $consulta = cache_query("SELECT * FROM textos  
                                WHERE clave = '$clave' AND lengua = '$lan'" ,"TRANSLATION_".$clave."_".$lan);


        if(mysql_num_rows($consulta)>0){
            while($item = mysql_fetch_array($consulta)){
                $this->id = $item['id'];
                $this->clave = $item['key'];
                $this->lengua = $item['language'];
                $this->texto = $item['text'];

            }
                return true;
         }
    }
    function get_text(){
          return $this->text;
    }
}
function translation($key,$language){
     $tem = new text($key,$language);
     return $tem->get_text();
}

then:

$translationText = translation('hello','fr');

The problem is that it stores in cache arrays (always zero), var_dump($m->get(k)) returns:

int(0) int(0) int(0) int(0) int(0) int(0) int(0) int(0) int(0) int(0) int(0) .....

And the $sql query is fine because the rows are collected fine and printed fine, the problem is with the stored value..

I have cleared the cache doing (several times, to make sure the values are not from a previous wrong output):

$consulta = $cache->get($nombre);
             /* manually*/
             $consulta = false;
        if ( $consulta === false) {
            $consulta = mysql_query($sql);
            $cache->set($nombre,$consulta, MEMCACHE_COMPRESSED, 60*60*24);
        };

so.. what am I missing?

EDIT

Here is a codepad, the problem is the mysql_query and memecache is not enabled, but in case someone wants to fiddle with it a bit

http://codepad.viper-7.com/PJNepH

Answer 1

The important thing to note is that you cannot store a result resource returned from mysql_query. I would recommend looping through the result set, fetching them with mysql_fetch_array, and then storing those objects in the cache.

Edit As PaulP.R.O. pointed out, the explicit serialize/deserialize were redundant.

$result = mysql_query($sql) or die("Query failed");

$results = array();

while ($array = mysql_fetch_array($result))
{
    $results[] = $array;
}

$cache->set($nombre, $results, MEMCACHE_COMPRESSED, 60*60*24);

When retrieving from memcached, simply use the unserialized array.

$cachedItem = $cache->get($nombre);

if ($cachedItem !== false) {
    var_dump($cachedItem);
}

Answer 2

You can only cache something that can be serialized. This includes everything but the type resource (which is returned from a successful mysql_query). You need to change your logic a bit so that you are caching an array. Change this:

$res = mysql_query($sql);
$cache->set($nombre,$res, 0, 60*60*24); 

To:

$res = mysql_query($sql);
$rows = array();
while($row = mysql_fetch_array($res)) $rows[] = $row;
$cache->set($nombre, $rows, 0, 60*60*24); 

Then change this:

if(mysql_num_rows($consulta)>0){
    while($item = mysql_fetch_array($consulta)){
        $this->id = $item['id'];
        $this->clave = $item['key'];
        $this->lengua = $item['language'];
        $this->texto = $item['text'];

    }
    return true;
}

To:

foreach($consulta as $item){
       $this->id = $item['id'];
       $this->clave = $item['key'];
       $this->lengua = $item['language'];
       $this->texto = $item['text'];
}

// This is your old code written to work with a 2D array instead of a resource,
// But this keeps overwriting the same variables in a loop,
// if you selected multiple rows; otherwise you don't even need a loop and can just do:

$this->id = $consulta[0]['id'];
$this->clave = $consulta[0]['key'];
$this->lengua = $consulta[0]['language'];
$this->texto = $consulta[0]['text'];

Answer 3

Memcache doesn't accept TTLs longer than 30 days. You can also use a ttl of 0 to set the key to never expire OR you set a ttl of less than 30 days.

eliminating memcached's 30-day limit

To create an easily serializable variable, you can do something like this.

$consulta = mysql_query($sql);   
while ($row = mysql_fetch_assoc($consulta)) {
  $data[] = $row;
}
$cache->set($nombre,$data, MEMCACHE_COMPRESSED, 60*60*24);