使用POSTMAN从JSON上传时，图像变空

Question

• I am trying to upload an image from JSON code. But when it is uploaded its data is stored in the folder. But data is lost(the file exist but has 0 bytes) I don't know if the problem is exactly from where. If anyone know please help me.

This is the code

 public function decodeImage($imageData)
   { 
    $imageData = $dat->imageData;
    $this->decodeImage($imageData); 
    $filename = "sampletest";
    $binary=base64_decode($imageData);
    header('Content-Type: bitmap; charset=utf-8');
    $file = fopen('./'.$filename, 'wb');
    fwrite($file, $binary);
    fclose($file);
    }