<?php
/**
 * Generates dynamic CSS styling based on user preferences stored in the session.
 * Specifically, it creates a CSS rule for the user's favorite color if it's specified in their session data.
 *
 * @return string Returns a string containing a `<style>` tag with custom CSS if a favorite color is set
 *                and the user is logged in. Returns an empty string if no conditions are met.
 */
function doDynamicStyling() :string
{
    $dynamic_style = "";
    if(isLoggedIn() && !empty($_SESSION["favorite_color"]) && is_int($_SESSION["favorite_color"]) && $_SESSION["favorite_color"] <= 4294967295){
        $dynamic_style = "<style>";
        $color = dechex($_SESSION["favorite_color"]);
        $dynamic_style .= "--root{ --favorite-color: #$color;";
        $dynamic_style .= "</style>";
    }
    return $dynamic_style;

}