To remove several options at once use pipe separated list.
<?php
$client = new GearmanClient();
$client->addOptions(GEARMAN_CLIENT_NON_BLOCKING | GEARMAN_CLIENT_FREE_TASKS | GEARMAN_CLIENT_UNBUFFERED_RESULT);
$client->removeOptions(GEARMAN_CLIENT_NON_BLOCKING | GEARMAN_CLIENT_FREE_TASKS);
?>