<?php

class Log()
{
    $protected writer = false;
    
    function __construct($writer)
    {   
        $this->write = $writer;
    }
    
    public function log($message)
    {
        if( ($message == "") || ($this->write == false) )
        {
            return;
        }
        
        $message = date("Y-m-d H:i:s")." - ".$message."rn";
        
        $this->writer->log($message);
    }
}



class fileWriter
{
    public function log($message)
    {
        file_put_contents("./fileWriter.log", $message, FILE_APPEND);
    }
}


class databaseWriter
{
    public function log($message)
    {
        $db->insert("log_table", array("message"), array($message) );
    }
}


// do some stuff

$oFileWriter = new fileWriter();

$oDatabaseWriter = new databaseWriter();


// log to file:

$oLog = new Log($oFileWriter);
$oLog->log("This logs to a file");


// log to database

$oLog = new Log($oDatabaseWriter);
$oLog->log("This logs to a database");