How to execute the Keep Both Files operation using PHP. Inspired by http://stackoverflow.com/a/14081609/80353

keep_both_files.php

<?php
  // you may also use pathinfo 
  // if the file you want to upload is already in the file directory
  // but not in the destination folder
  $file_to_upload = 'test.png';
  // either way, you definitely need to retrieve the filename and extension
  $filename = 'test';
  $extension = 'png';
  // feel free to change the destination path
  $destination_path = dirname(__FILE__);
  
  // initialize the new filename as the actual name of the file_to_upload
  $new_filename = $filename;
  $i=0;
  while(file_exists($destination_path . DIRECTORY_SEPARATOR . $new_filename . "." . $extension)) 
  {
    $new_filename=$filename . " ($i)";
    $i++;
  }
  $new_file = $new_filename . "." . $extension;
  echo $new_file;
?>