For those of you new to PHP and those of you who haven’t run into this problem already, here are a few pointers about the Cannot modify header information – headers already sent error and some things that might work for you to fix them

There are several reasons to modify the header values, for example if you want PHP to generate XML output, you would want to modify the header information.
Often people stumble into this error when using the header() function in PHP.

Let’s look at few ways to try and fix this error.

First thing lets get some debugging output to help us

<?php
ini_set(‘display_errors’, true);
ini_set(‘display_startup_errors’, true);
error_reporting (E_ALL);
?>

Check your PHP file for whitespaces and blank lines before the <?php tag and after the ?> tag. There should be no whitespaces or blank lines outsides those tags.
Note! Dreamweaver used to addwhitespaces to .php files saved as UTF-8, but they are invisible in Dreamweaver.

You can add this line to the very start of your script.

<?php ob_start(); ?>

You can add the following line to your php.ini file

output_buffering = 4096

Check your files encoding settings.

These are the problems I’ve personally ran into with this error and hopefully this can help you if you are having the same problem.

Munin is a nice tool to monitor your Linux server.
It can show you a whole lot of information in graphs, and everybody likes graphs! They look cool and sometimes they even give you some information!

If you are running Ubuntu / Debian, it’s extremely simple to set up Munin and get it running.

Let’s assume that we have a server called nerdrage.org and we want to monitor that.

First we install Munin using apt-get

sudo apt-get install munin munin-node

With munin and munin-node installed, we would like to edit the configuration file which is in /etc/munin/munin.conf.
From here we can set the output directory and we also want to set a server name.

vi /etc/munin/munin.conf

Here we want to change htmldir (this is where munin puts the fancy graphs) and we also want to change [server1.example.com] to your own server name (for example www.nerdrage.org).
The rest of the settings we don’t have to worry about at this point.

dbdir   /var/lib/munin
htmldir /var/www/www.nerdrage.org/munin
logdir  /var/log/munin
rundir  /var/run/munin

tmpldir /etc/munin/templates

[server1.example.com]
    address 127.0.0.1
    use_node_name yes

Then we create the output directory for munin

sudo mkdir /var/www/www.nerdrage.org/munin

And change the ownership so munin can write to the directory

sudo chown munin:munin /var/www/www.nerdrage.org/munin

And finally we restart the service

sudo /etc/init.d/munin-node restart

After a few minutes you can go to the address that you specified in the configuration file (in this case http://www.nerdrage.org/munin) and see some fancy graphs!

Til hamingju með afmælið mamma!

Our server managed to crash, so I’m rebuilding the whole thing now.

Most of the stuff is recoverable, but sadly the one thing that isn’t is the code I’ve been writing for the past 2 months. Purrhaps I’ll be a bit more careful next time, eh?

Back to installing services! Ciao!