unity crash when upload a file

Hi...

I created an application to upload files to my server .

on android when I upload a file more than 13 mb . the unity crash and close .

but when I use the same application on Editor , it's work fine ..

what should I do ?

upload code :

         WWWForm postForm = new WWWForm();
         postForm.AddBinaryData("theFile",localFile.bytes,FilePath,"");
         upload = new WWW(UploadPHP,postForm);
         yield return upload;

php file

     $folder = "../Uploaded/";
     if (is_uploaded_file($HTTP_POST_FILES['theFile']['tmp_name']))
     {
         if (move_uploaded_file($HTTP_POST_FILES['theFile']['tmp_name'], $folder.$HTTP_POST_FILES['theFile']['name']))
         {
             Echo 1;//'File uploaded';
         }
     }
     else
     {
         Echo 0;//'File is not uploaded.';
     };

thanks ....