[RESOLVED] fwrite writing multiple entries

[echosix]

Hi,
I'm writing tracking information for my website to a file using PHP. 99% of the time it works, but occasionally I get an odd entry, where it looks like fwrite() is called more than once simultaneously, so that two entries get blended into one. Since the lines are very long, I put an example of several correct entries and an incorrect one at:

http://www.sfu.ca/~kganapat/example.html

As you can see, it looks on the 3rd line, each fwrite() is called twice. The PHP script is called via javascript (hence the $_GET's). Here's the code:

<?

$userIP = $REMOTE_ADDR;
$userURL = $HTTP_REFERER;
$userURLj = $_GET['page'];
$userAgent = $HTTP_USER_AGENT;
$userRef = $_GET['ref'];
$dateTime = date('Y/m/d g:i:s A');

$fileName = "visitorData.txt";

$fileHandle = fopen($fileName, 'a') or die("can't open file");

fwrite($fileHandle, $dateTime);
fwrite($fileHandle, " - ### - ");
fwrite($fileHandle, $userIP);
fwrite($fileHandle, " - ### - ");
fwrite($fileHandle, $userURL);
fwrite($fileHandle, " - ### - ");
fwrite($fileHandle, $userRef);
fwrite($fileHandle, " - ### - ");
fwrite($fileHandle, $userURLj);
fwrite($fileHandle, "\n");

fclose($fileHandle);


$lines = file('visitorData.txt');

?>

Any ideas on why this would happen?

I'm thinking that the script is somehow called twice simultaneously, so that two instances of the same script are running at the same time. If this is the case, any tips on how to simulate a lock so that two different instances of the script can't write to the file at the same time?

Thanks!

[laserlight]

If this is the case, any tips on how to simulate a lock so that two different instances of the script can't write to the file at the same time?

You can use [man]flock/man.

[bradgrafelman]

Also not that you could condense all of those fwrite()'s into one - just use concatenation (or even variable interpolation - just put the variables inside a string delimited by double quotes).

EDIT: In addition, you shouldn't be using the '<?' short tags as they have been deprecated for a while; instead, use the full '<?php' tags. While we're talking about deprecated practices, you should look into disabling register_globals as it's long since been recognized as a security exploit and isn't even available in PHP6. As such, instead $REMOTE_ADDR, you should be using $_SERVER['REMOTE_ADDR']. More information on these superglobal arrays can be found here: [man]variables.predefined[/man].

[echosix]

thanks! I'm still not sure why the problem existed in the first place, but doing it this way is much better and hopefully will fix the problem. And thanks for the extra tips... I've learned something today 🙂

[bradgrafelman]

Don't forget to mark this thread resolved (if it is).