<?php namespace CouchBaseWrapper;
 use CouchbaseCluster;

class CouchDB {
    private $couchClient;
    private $couchBucket;

    private function openConection(){
        try{
            $this->couchClient = new CouchbaseCluster(<COUCH_HOST>);
            $this->couchBucket = $this->couchClient->openBucket(<COUCH_BUCKET>);
        }
        catch (Exception $e) {
            echo $e;
        }
        return true;
    }

    function getKey($k) {
        try{
            if(!$this->openConection()) { return false; }

            $res = $this->couchBucket->get($k);
            $data_rcvd = $res->value;
        }
        catch(Exception $e){
            echo $e;
        }
        echo "Outter Code";
        return $data_rcvd;
    }

}
?>

<?php namespace CouchBaseWrapper

ini_set("display_errors", true);

require_once('couchbaseWrapper.php');

$cb = new CouchDB();
$result = $cb->getKey("non-existing-key"); // <== Error
//$result = $cb->getKey("existing-key");   // <== Existing key No error

var_dump($result);
?>

public function exists($key) {
    if(!$this->openConection()) { return false; }
    return $this->couchBucket->get($key) == NULL
    && $this->couchBucket->getResultCode() == COUCHBASE_KEY_ENOENT;
}

try{
        // ...
    }
    catch(Exception $e){
        echo $e;
    }

try{
        // ...
    }
    catch(CouchBaseWrapperException $e){
        echo $e;
    }

try{
        // ...
    }
    catch(Exception $e){
        echo $e;
    }