new message every day

I have had a different message appearing evry day based on the name of the day. I now want a message based on the date up to 31. I have tried messing to no no avail. Help will be appreciated

$day_post = "includes/days";
 
$today = date('l');
if (file_exists($day_post."/".$today.".php"))
    {   
    /**echo "$day_post/".$today.".php"; **/
include("$day_post/".$today.".php");
    } else {   
    echo "No thoughts came into my head $today";
}