上载图像PHP-验证ISSET时出错

我按照链接将图像从android上传到服务器。但是PHP部分的上传失败了，所以我添加了一些echo来跟踪是哪一个触发了错误。我发现，即使我已经设置了要上传的图像（我使用Postman），也会触发“请选择文件”错误

<?php 

     //importing dbDetails file 
     require_once('dbDetails.php');

     //this is our upload folder 
     $upload_path = 'uploads/';

     //Getting the server ip 
     $server_ip = gethostbyname(gethostname());

     //creating the upload url 
     $upload_url = 'http://xxx/xxx/'.$upload_path; 

     //response array 
     $response = array(); 


     if($_SERVER['REQUEST_METHOD']=='POST'){
        echo "method OK";

     //checking the required parameters from the request 
         if(isset($_POST['name']) && isset($_FILES['image']['name'])){
            echo "isset ok";

             //connecting to the database 
             $con = mysqli_connect(HOST,USER,PASS,DB) or die('Unable to Connect...');

             //getting name from the request 
             $name = $_POST['name'];

             //getting file info from the request 
             $fileinfo = pathinfo($_FILES['image']['name']);

             //getting the file extension 
             $extension = $fileinfo['extension'];

             //file url to store in the database 
             $file_url = $upload_url . getFileName() . '.' . $extension;

             //file path to upload in the server 
             $file_path = $upload_path . getFileName() . '.'. $extension; 

             //trying to save the file in the directory 
                 try{
                     //saving the file 
                     move_uploaded_file($_FILES['image']['tmp_name'],$file_path);
                     $sql = "INSERT INTO uploads (id, fileUpload, name) VALUES (NULL, '$file_url', '$name');";

                     //adding the path and name to database 
                     if(mysqli_query($con,$sql)){

                     //filling response array with values 
                     $response['error'] = false; 
                     $response['url'] = $file_url; 
                     $response['name'] = $name;
                     }
                     //if some error occurred 
                 }catch(Exception $e){
                     $response['error']=true;
                     $response['message']=$e->getMessage();
                 } 
             //displaying the response 
             echo json_encode($response);

             //closing the connection 
             mysqli_close($con);
         } else{
            echo "isset error";
             $response['error']=true;
             $response['message']='Please choose a file';
         }
     }

     function getFileName(){
     $con = mysqli_connect(HOST,USER,PASS,DB) or die('Unable to Connect...');
     $sql = "SELECT max(id) as id FROM uploads";
     $result = mysqli_fetch_array(mysqli_query($con,$sql));

     mysqli_close($con);
     if($result['id']==null)
     return 1; 
     else 
     return ++$result['id']; 
     }
?>