我有表调用用户，例如

id name amount   created 
1   a   100     6-16-2016 
2   b   200     5-16-2016 

  $user = $this->Users->find('all',[ 
         'fields' => array('MAX(Users.amount)  AS amount'), 
  ]);  

请您参考如下方法:

最简单的方法

$user = $this->Users->find('all',[ 
   'fields' => array('amount' => 'MAX(Users.id)'), 
]);  

$user = $this->Users->find() 
    ->select(['amount' => 'MAX(Users.id)']);  

$query = $this->Users->find(); 
$user = $query 
    ->select(['amount' => $query->func()->max('Users.id')]); 

$user = $user->first(); 
$amount = $user->amount;