cas() operation does not check if the cas contains illegal characters.

$cb = new \Couchbase('127.0.0.1', '', '', 'default', true);

$cas = $cb->set('foo', 'bar', 0, null);
var_dump($cb->get('foo'));

var_dump($cb->cas($cas, 'foo', 'baz', 0));
var_dump($cb->get('foo'));

var_dump($cb->cas($cas, 'foo', 'bad', 0));
var_dump($cb->get('foo'));

var_dump($cb->cas('This is an invalid CAS', 'foo', 'bar', 0));
var_dump($cb->get('foo'));

RESULTS OF RUNNING:
php test.php
string(3) "bar"
bool(true)
string(3) "baz"
bool(false)
string(3) "baz"
bool(true)
string(3) "bar"