Use hexadecimal notation.

lib/Predis/Cluster/Hash/CRC16HashGenerator.php

@@ -64,7 +64,7 @@ class CRC16HashGenerator implements HashGeneratorInterface
         $strlen = strlen($value);
 
         for ($i = 0; $i < $strlen; $i++) {
-            $crc = (($crc << 8) ^ $CCITT_16[($crc >> 8) ^ ord($value[$i])]) & 65535; // 0xFFFF
+            $crc = (($crc << 8) ^ $CCITT_16[($crc >> 8) ^ ord($value[$i])]) & 0xFFFF;
         }
 
         return $crc;