How to sequence events while uploading large files to Amazon S3?

Question

I am seeing problems uploading large files e.g. 100MB. Files go to Amazon S3 successfully, but after that scripts are waiting for if($flag == 1) and do not execute the rest of the code. Can anyone tell me the solution for this?

if($s3->putObjectFile($uploadDIR, $bucket, $name, S3::ACL))
{
      $flag = 1;
}

if($flag == 1)
{
      //continue code
}