// A module to write out events to a set of log files. Similar to error_log(),
// but with multiple output files.
//
// You'll need to set up a directory that the process running PHP (eg Apache) has
// permission to write to. You'll also need to keep an eye on the size of the log
// files, rotate out old ones once they get too large, etc.
//
// By Pete Warden ( http://petewarden.typepad.com ) – freely reusable with no restrictions

// Edit this to set it to the folder on your server where you want the logs to live
//define('CUSTOM_LOG_ROOT_DIRECTORY', '/private/var/log/apache2/'); // OS X default Apache log directory
define('CUSTOM_LOG_ROOT_DIRECTORY', '/var/log/httpd/'); // Red Hat Linux default Apache log directory

$g_custom_log_categories = array();
$g_custom_log_shutdown_registered = false;

// This function works like error_log(), but takes an extra category argument that
// determines which file the message is appended to.
function custom_log($category, $message)
{
    global $g_custom_log_categories;
   
    // If the file hasn't been opened for appending yet, create a new file handle
    if (!isset($g_custom_log_categories[$category]))
    {
        // Make sure there's no shenanigans with special characters like ../ that
        // could be abused to write outside of the specified directory
        $sanitizedcategory = preg_replace('/[^a-zA-Z0-9]/', '_', $category);
        $filename = CUSTOM_LOG_ROOT_DIRECTORY.$sanitizedcategory;
        $filehandle = fopen($filename, 'a');
        if (empty($filehandle))
        {
            error_log("Failed to open file '$filename' for appending");
            return;
        }

        // To close any open files once the script is done, and so ensure that
        // all the messages are written to disk, register a global shutdown
        // function that fclose()'s any open handles
        global $g_custom_log_shutdown_registered;
        if (!$g_custom_log_shutdown_registered)
        {
            register_shutdown_function('custom_log_on_shutdown');
            $g_custom_log_shutdown_registered = true;
        }
       
        // Urghh, this is required to prevent a spew of warnings when more recent
        // PHP versions are set to strict errors
        if (!ini_get('date.timezone'))
            date_default_timezone_set('UTC');
       
        $g_custom_log_categories[$category] = array('filehandle' => $filehandle);
    }

    // Create the full message and append it to the file
    $categoryinfo = $g_custom_log_categories[$category];   
    $filehandle = $categoryinfo['filehandle'];
   
    $timestring = date('D M j H:i:s Y');
    $ipaddress = $_SERVER['REMOTE_ADDR'];
    $fullmessage = "[$timestring] [$category] [client $ipaddress] $message\n";
   
    fwrite($filehandle, $fullmessage);
}

// A clean-up function called to make sure all open file handles are closed
function custom_log_on_shutdown()
{
    global $g_custom_log_categories;
    foreach ($g_custom_log_categories as $category => $categoryinfo)
        fclose($categoryinfo['filehandle']);
}