<?php
// first we declare a class to handle the file operations.
class logfile{
function write($logString )
{
    if( $handle = @fopen( '../logs/actionLog.txt', 'a+' ) ) 
    // this can be parameratized
    {
        $logString .="\n"; // insures each entry is on a new line
        fputs( $handle, $logString, strlen($logString) );
        fclose( $handle );
        return( true );
    }
    else
    {
        return( false );
    }
}
} // end logfile class

function logAction($job,$cd,$msg)
{
    // now we can create the custom code using the class
    $msgTypes=explode(',',"INFO,PROGRESS,WARN,ERROR,SECURITY,INVALID"); 
    //invalid must always be the last entry ... add more if needed
    $cod = ($cd>=count($msgTypes)) ? (count($msgTypes) - 1) : $cd;
    // If the code is invalid return INVALID as the message type
    $dt=date("Y-m-d H:i:s"); 
    // customize the date format to fit your requiremments
    $theLog = new logfile();
    // an instance of the logfile class
    $msgStr=$msgTypes[$cod].'{'.$cd.'}: '.$job.': '.$dt.'>>> '.$msg; 
    // create the log message
    $theLog->write($msgStr); // this fires the file handling in the class
}
?>

http://coboldinosaur.com/pages/Custom_Logging_Site_Events.html

To keep up on important incidents on your site without having to dig through server logs the alternative can be custom logs.

Custom Logging Site Events

security

PHP