title: Check if a key exists in Memcache
body: <p>How do I check in PHP if a value is stored in Memcache without fetching it? I don't like fetching it because the values I have set are all 1MB in size and after I fetch it, I have no use for it, so I'm wasting resources. I'm using this in a script that checks if certain keys are cached in memcache and if not, it reads them from a slow data source and sets them in memcache.</p>
  
  <p>Edit: What if I use <code>Memcached::append</code> to append <code>NULL</code> to the key I'm checking? Returns <code>TRUE</code> on success or <code>FALSE</code> on failure. The <code>Memcached::getResultCode</code> will return <code>Memcached::RES_NOTSTORED</code> if the key does not exist. This way I check whether the key exists and it should put the key on top of the LRU list right?</p>
  
  <p>Thank you.</p>