问exec('ping')在开发服务器上工作，但在生产中不工作

EN

public function testDomain(){
    if($this->request->is('post')){
        $ip = $this->request->data['domain'];

        $starttime = microtime(true);

        $stoptime  = microtime(true);
        $total_time = ($stoptime - $starttime) * 1000;

        exec("ping -n 3 $ip", $output, $status);
        print_r($status);
        if (0 == $status) {
            echo $mode = 'up';
            if($total_time <= '500'){
                $result =  'Very Fast';
            }else if($total_time <='1000'){
                $result = 'Fast';
            }else if($total_time <='1500'){
                $result ='Good';
            }else if($total_time <='2500'){
                $result ='Slow';
            }else if($total_time <='3000'){
                $result ='Very Slow';
            }else{
                $result ='down';
            }
            echo $ip.'  '.'is'.'  '.$result; 
        }else{
            echo $mode = 'down';

        }        
    }   
    exit;
}