Creating a file based log system

If we have a website we would certainly want to know the impressions of our website visitors. 

In addition to knowing about information of visitors, a log file is also useful to help analyse the security.

I will go directly to explain the log system file in PHP script: 

<?php 

// checking the bowser's type 

$agent = $_SERVER ['HTTP_USER_AGENT']; 

// * checking where the script is executed from -- GET (URL) 

$uri = $_SERVER ['REQUEST_URI']; 

// * checking visitor's IP 

$ip = $_SERVER ['REMOTE_ADDR']; 

/ * checking where the script is referred from 

$ref = $_SERVER ['HTTP_REFERER']; 

// * checking visitor's proxy

$original = $_SERVER ['HTTP_X_FORWARDED_FOR']; 

// * checking visitor's connection 

$via = $_SERVER ['HTTP_VIA']; 

// * variable date 

$dtime = date ('r'); 

// * note if  visitors use transparent Proxy 

// * Then the $_SERVER ['HTTP_X_FORWARDED_FOR'] will display the visitor's IP 

// * otherwise $_SERVER [ 'REMOTE_ADDR'] will display the Proxy 

// * For clear about Proxy i will explain in another tutorial 

// * This is a description of variable entry_line: 

$entry_line = "Time: $dtime | Original IP: $ip | Browser: $agent | URL: $uri | referrer: $ref | Proxy: $original | Connection: $via 

";   // * <- Attention! This must be a new line or you press enter to create a new line 

/ * "fopen ()" function for opening files, "a" is the most important.!, 

/ * This works if the file "trace.txt" does not exist in the server then PHP will create 

$fp = fopen ( "trace.txt", "a"); 

/ /* "fputs ()" function for writing into the log file 

fputs ($fp, $entry_line); 

// * "fclose ()" function to close the file 

fclose ($fp); 

?> 

This file based log system using php function is pretty useful instead of using mysql connection