TYPO3 Core

None of my own extensions and project-specific code uses the has() function.
Unfortunately, there a lot of code spread around in Typo3 and 3rd party extensions that seems to use the has() function of the caching framework.
When I introduced the has()-buffer, I've seen the number of calls to memcached drop by about 30% on fully-cached pages.

I've added some documentation for extension developers about has() to the wiki page. Feel free to improve it (at bottom of the page).

Thanks for the documentation addition.

Unfortunately, I disagree with the point has() is not used widely.

Take a look at Tx_Extbase_Object_Container_Container->getClassInfo()
This function, for my project is called over 2500 times.

Just take a look at the "if" parts:

private function getClassInfo($className) {
    if (!$this->cache->has($className) || !is_object($this->cache->get($className))) {
        $this->cache->set($className, $this->classInfoFactory->buildClassInfoFromClassName($className));
    }
    return $this->cache->get($className);
}

Only for the "if", we get 3x more calls to cache (memcached for my project).
That's 3 calls, including the return's get(), instead of the one required.

When I implemented the has()-buffer, I managed to save A LOT of calls to memcached... and that was not only from the above function...

Seriously, if the Extbase team is using this function... I guess other are too...

And, on similar note, I just noticed the t3lib_cache_backend_DbBackend->has() is doing a COUNT on the DB's tables.
Most extensions that uses caching framework are pre-configured to use the Db-Backend?
That's two call to the db for a hit in the cache!
At least, it was for Extbase on my project...

The above method is obviously unclever and should be optimized ... would you like to create a issue and patch for that in the mvc list and maybe push it to gerrit right away?

At first glance something like that should do:
$myObject = $cache->get()
if (!is_object($myObject)) {
$myObject = $doMagic();
$cache->set($myObject, ...);
}
return $myObject;

I'll do.
This was the first "->has(" search result my IDE gave me back... there is still a lot around.. so, my point on the presence/implementation of the has() method still applies ;)