Populate drop-down list with usernames

function populate_userdrop($form){

    //only populating drop down for form id 1
    if($form["id"] != 1)

    return $form;

    //Creating item array.
    $items = array();
    // Get the custom field values stored in the array
    $meta = get_users();

if (is_array($metas))
{
foreach($metas as $meta)  $items[] = array("value" => $meta->display_name, "text" => $meta->display_name);
}
    //Adding items to field id 1. Replace 1 with your actual field id. You can get the field id by looking at the input name in the markup.
    foreach($form["fields"] as &$field)
        if($field["id"] == 1){
            $field["choices"] = $items;
        }

    return $form;
}

// This adds display names for all users to a drop down box on a gravity form.
add_filter("gform_pre_render", "populate_userdrop");

//Note: when changing drop down values, we also need to use the gform_admin_pre_render so that the right values are displayed when editing the entry.
add_filter("gform_admin_pre_render", "populate_userdrop");

function populate_userdrop($form){

    //only populating drop down for form id 1 - if editing this change to your own form ID
    if($form["id"] != 1)

    return $form;

    //Creating item array.
    $items = array();
    // Get the custom field values stored in the array
	// If editing this lookup where you would like to get your data from
	// this example loads through all users of the website
    $metas = get_users();

if (is_array($metas))
{
// in this example we just load the display_name for each user into our drop-down field
foreach($metas as $meta)  $items[] = array("value" => $meta->display_name, "text" => $meta->display_name);
}
    //Adding items to field id 1. Replace 1 with your actual field id. You can get the field id by looking at the input name in the markup.
    foreach($form["fields"] as &$field)
        if($field["id"] == 1){
            $field["choices"] = $items;
        }

    return $form;
}