离子订阅返回“错误”，但PHP响应是“成功”

We are using subscribe method in our home.ts. Once the data is saved php file response is "Success".

On Windows browser (Chrome) result is as expected, but on Android or Mac Chrome, response is "success" from php, but on Ionic side it returns "err". File is uploaded but instead of success it says err

Below is my home.ts code

let form = new FormData();
    form.append("file", this.filenm);
    this.httpclient.post<any>("http://example.com/test/upload.php",form)
    .subscribe((res)=>{
      console.log(res,'res');
      if(res == 'Success')
      {
        console.log('Image uploaded sucessfully.');
      }
      else
      {
        console.log('Please try again later.');
      }
    },err=>{
      console.log(err,'err');
    });