An example of using an SQL Expression in Zend\Db\Sql

select-count.php

/**
 * First construct the Select object for the SQL query to run
 */
$select = new Select('tblusers'); 
$select->columns(array( 
  "recordCount" => new \Zend\Db\Sql\Expression("COUNT(*)") 
));

/**
 * Then execute the query, retrieving the first record, if available
 * This uses the RowGateway class <http://framework.zend.com/manual/2.0/en/modules/zend.db.row-gateway.html>
 */
if (!$row = $this->tableGateway->selectWith($select)->current()) {           
  throw new RecordSearchException("Could not find row $feedId");       
} 

/**
 * Show the value of recordCount
 */
print $row->recordCount;