public function countMessages($cb, $flags = null)
{
$this->onResponse->push($cb);
if ($flags === null) {
$this->searchMessages(['ALL'], self::TAG_COUNT);
return;
}
$params = [];
foreach ((array) $flags as $flag) {
if (isset($this->searchFlags[$flag])) {
$params[] = $this->searchFlags[$flag];
} else {
$params[] = 'KEYWORD';
$params[] = $this->escapeString($flag);
}
}
$this->searchMessages($params, self::TAG_COUNT);
}