Rename the files while uploading

I am trying to rename the files while uploading, but it's not renaming as I expected. Just want to add the date and the time front of the name.

Attaching the code below.

if(isset($_FILES['img_ct_1'])){



$today = date("Ymd");



//prepare url

$temp_path = CDN_URL.'photos/';



$name_array = $_FILES['img_ct_1']['name'];

$tmp_name_array = $_FILES['img_ct_1']['tmp_name'];

$type_array = $_FILES['img_ct_1']['type'];

$size_array = $_FILES['img_ct_1']['size'];

$error_array = $_FILES['img_ct_1']['error'];

$upload_dir = $_SERVER['DOCUMENT_ROOT'].'/photos/';





for($i = 0; $i < count($tmp_name_array); $i++){

    if(move_uploaded_file($tmp_name_array[$i],$upload_dir.time().$name_array[$i])){

        print_r ($name_array[$i]);

        $array['path'] = $temp_path.$newfilename;

        $array['success'] = true ;

    } else {

        echo "move_uploaded_file function failed for ".$name_array[$i]."<br>";

    }

}

}