magento_custom_log.php

<?php 

const LOG = 'my.log';

/**
* @return void
* @param $var The variable passed
* @param string $label
* @param boolean $backtrace
*/
public function log($label,$var=null,$backtrace = false)
{
    if($backtrace){
        $ouput = str_replace(array('<pre>','</pre>'),'',Varien_Debug::backtrace(true, true));   

    }else{
        $d= debug_backtrace();
        $level = 0;
        $file = !isset($d[$level])?'':$d[$level]['file'];
        $line = !isset($d[$level])?'':$d[$level]['line'];
        $infoline = $file.' - '.$line.': ';
        if($var){
            $message = $infoline.$label.': ';
            $iouput = Zend_Debug::dump($var,$message,false);
            $ouput = htmlspecialchars_decode(str_replace(array('<pre>','</pre>'),'',$iouput));
        }else{
            $ouput = $infoline.$label;
        }
    }
    
    Mage::log($ouput, null, self::LOG);
}