PHP Function visitorPreviousPage() to Get Visitors Previous Page Url

PHP Function visitorPreviousPage() to Get the URL of the Page Visitor Just Came from/Previous Page

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/* --------------------------------------------------------------
  * function to get page person just came from/previous page url
  * ---------------------------------------------------------- */
function visitorPreviousPage(string $defaultPage) 
{
    # Static variable to store the previous page value within the same request
    static $previousPage = null;

# Construct the full URL for the current page
    $scheme = isset($_SERVER['HTTPS']) && $_SERVER['HTTPS'] === 'on' ? 'https' : 'http';
    $host = $_SERVER['HTTP_HOST'];
    $currentPage = $scheme . '://' . $host . $_SERVER['REQUEST_URI'];

# On the first call, initialize $previousPage based on the priority order
    if ($previousPage === null) 
    {
        # Priority 1: Fetch from session if available
        if (isset($_SESSION['previous_page']) && !empty($_SESSION['previous_page'])) 
        {
            $previousPage = $_SESSION['previous_page'];
        }

# Priority 2: Fetch from HTTP_REFERER if available and valid
        elseif (isset($_SERVER['HTTP_REFERER']) && strpos($_SERVER['HTTP_REFERER'], $_SERVER['HTTP_HOST']) !== false) 
        {
            $previousPage = $_SERVER['HTTP_REFERER'];
        }

# Priority 3: Use default page
        else 
        {
            $previousPage = $defaultPage;
        }

# Update the session with the current page URL
        $_SESSION['previous_page'] = $currentPage;
    }

else 
    {
        # Update the session with the current page URL
        $_SESSION['previous_page'] = $currentPage;
    }

return $previousPage;
}

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