First in mymodule.install I declared mymodule_schema(hook_schema) mymodule_install() and mymodule_unistall()

Where mymodule_schema() is like this:

function mymodule_schema() {
    $schema = array();
    $schema['cache_mymodule'] = drupal_get_schema_unprocessed('system', 'cache');
    return $schema;

this worked perfectly and table cache_mymodule with the same structue as table cache was created.
But in my code, using this:

if (!$cache){
    $data = some_calcuated_data();
    dpm('CACHE SET');
else {
    dpm('used cache');

I always get 'CACHE SET', Now if i change 'cache_mymodule' to just cache, Or remove it, It works perfectly (saying used cache), Am I missing some hook in mymodule?

  • 1
    Since Drupal 7, you no longer need to drupal_install_schema on hook_install to add necessary tables. it will be done for you automagically.
    – AKS
    Nov 8, 2012 at 18:35

3 Answers 3


It looks like the problem is just a misnamed variable.


$data = some_calcuated_data();

should be

$data = some_calcuated_data();
cache_set($cid, $data, 'cache_mymodule');

At the moment you're setting the cache as NULL, any time it's already NULL...probably not what you were going for :)

  • fixed it, tnx, but it's correct in actual module
    – hkoosha
    Nov 7, 2012 at 16:59
  • Hmm very strange, I use exactly the same pattern all the time and I've never had a problem. Have you tried hardcoding a $cid to see if it's a problem with the id generation function?
    – Clive
    Nov 7, 2012 at 18:26
  • sorry Clive! really! you were right... sometimes people make crazy mistakes
    – hkoosha
    Dec 6, 2012 at 13:16

You don't need to create your own table to use the internal cache. Just use cache_set() and cache_get() as documented. This will store the $my_data in the default 'cache' table:

// Store $my_data in cache.
cache_set($data_id, $my_data);

// Get $my_data from cache.
$data = cache_get($data_id);

Your code snippet should look something like this:

$cid = some_calcuated_cid();
$cache = cache_get($cid);

if (!$cache){
  $data = some_calcuated_data();
  cache_set($cid, $data);




  • 4
    You can create custom cache tables if needed, no issues in that.
    – GoodSp33d
    Nov 7, 2012 at 7:07
  • i know but i want to learn creating my own cache, tnx for the tip
    – hkoosha
    Nov 7, 2012 at 16:56
  • Nothing wrong with that. I do realize I answered a bit beside the actual question. I would suggest you break things apart and make sure your variables contain correct data.
    – enzipher
    Nov 7, 2012 at 20:43

In order to debug this, enable the mysql log which displays all queries executed (you will need a mysql restart)

mysqld.exe --log=path\to\log\file\your-log-file-name.log

This will give you a clue if the respective sql insert command is actually triggered and executed. And you should also check (via sql) if 'cache_mymodule' is empty or not after the code snippet execution.

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