azure-storage-queue/src/Queue/QueueRestProxy.php
public function clearMessages($queueName, QueueServiceOptions $options = null)
    {
        $this->clearMessagesAsync($queueName, $options)->wait();
    }
public function clearMessages($queueName, QueueServiceOptions $options = null)
    {
        $this->clearMessagesAsync($queueName, $options)->wait();
    }
Clears all messages from the queue.

If a queue contains a large number of messages, Clear Messages may time out
before all messages have been deleted. In this case the Queue service will
return status code 500 (Internal Server Error), with the additional error
code OperationTimedOut. If the operation times out, the client should
continue to retry Clear Messages until it succeeds, to ensure that all
messages have been deleted.

@param string              $queueName The name of the queue.
@param QueueServiceOptions $options   The optional parameters.

@return void