logger.php

<?php
class Logger {
    private static $file = '../log/app.log';

    private static function log($level, $msg) {
        $keys = array(
            'HTTP_HOST',
            'REDIRECT_STATUS',
            'REQUEST_METHOD',
            'REMOTE_ADDR',
            'HTTP_VIA',
            'HTTP_X_FORWARDED_FOR',
            'HTTP_USER_AGENT',
            'HTTP_X_VARNISH',
            'HTTP_ACCEPT',
            'HTTP_ACCEPT_LANGUAGE',
            'REQUEST_URI',
            'QUERY_STRING'
        );  

        foreach ($keys as $key) {
            if (array_key_exists($key, $_SERVER) && !empty($_SERVER[$key]))
                $params[$key] = $_SERVER[$key];
        }   

        $log = '"' . join("\" \"", $params) . '"';

        if (!empty($msg))
            $log .= ' "' . $msg . '"';

        $f = fopen(self::$file, 'a');
        fwrite($f, sprintf("%s [%s] %s\n", date("Y-m-d H:i:s"), $level, $log));
        fclose($f);
    }   

    public static function error($msg = '') {
        self::log('error', $msg);
    }   

    public static function warn($msg = '') {
        self::log('warn', $msg);
    }   

    public static function info($msg = '') {
        self::log('info', $msg);
    }   

    public static function debug($msg = '') {
        self::log('debug', $msg);
    }   
}
?>