Rename file before uploading it (Dana)

<?php
//assumes form id 118
add_action("gform_pre_submission_118", "change_filename");
function change_filename($form){
    //note, the current filename is stored in the $_FILES object in an array named using the input field name
    //in my test, my upload field was field id 2, so it is input_2
    $uploaded_name = $_FILES["input_2"]["name"]; //get current filename, do something with it
    $uploaded_name = "mytest.txt"; //changing filename
    //replace name in files global
    $_FILES["input_2"]["name"] = $uploaded_name;
}