Jani: IIRC there was some Apache configuration thing that might interfere with this. (Note: This is reminder for myself, ignore :)

Couple of questions: What was the configure line used to configure PHP?
What Aapche MPM are you using? What PHP SAPI? Do you set any php.ini options in some .htaccess file or in your httpd.conf? Check the phpinfo() output 

I apologize for the delay, I was abroad.

I've recompiled Apache. It's 2.2.8 now but it has the same problem. I've also tried to downgrade PHP (to 5.2.3) but nothing...

Everything happens under CPANEL and WHM cpeasyApache so I don't understand "What Apache MPM are you using? What PHP SAPI?" questions.

Php.ini is altered only to increase maximum size of uploaded file etc. but not by hand. There are some checkboxes and textboxes in cpanel's WHM.

.htacces is not altered.

I'm just recompiling (I try to find the common elements which may point out the problem). When finished I'll copy/paste the phpinfo()

Please don't add full phpinfo() output here but rather a link to a place where the info can be seen.

phpinfo:
http://www.alfavita.gr/myphp.php 

testing page:
http://www.alfavita.gr/errata.php

In the new compile I've lowered limits to 8M in case it would do any good (it didn't).

Neither of those links work.

I'm sorry to say that but ...you have some problem with your conection. Just to be sure I've tried the links with www.megaproxy.com and they work allright all over the world. It might have to do something with your firewall. Please try again or use www.megaproxy.com 
phpinfo:
http://www.alfavita.gr/myphp.php 

testing page:
http://www.alfavita.gr/errata.php

What if you try this script as target.php:

<?php var_dump($_REQUEST); ?>

And usually using proper HTML (With quotes around parameter values) helps too. 

Aw it concerns HTML quotes: 
a) It doesn't work either way
b) I remind you that this is a bug report and not a "I can't program" report.

The very same code works in other servers. e.g.:
http://www.xpert.gr/errata.php
Please note that this server runs on PHP 4.3.9 which is no longer supported. Please read http://www.xpert.gr/myphp.php in order to compare php infos

I've added the variable dumbing to target.php as you've said but it's still null on PHP 5.2.5 Apache/centos server and works fine on PHP 4.3.9 server

Netcraft's report :
Problematic server: Apache/2.2.8 Unix mod_ssl/2.2.8 OpenSSL/0.9.8b mod_auth_passthrough/2.1 mod_bwlimited/1.4 FrontPage/5.0.2.2635 mod_jk/1.2.25 PHP/5.2.5

Is it possible that the problem maybe caused by CENTOS since the working server runs REDHAT? Can you crossreference or even prove such an assumption?

(be careful: I'm just guessing)

I assume that something conflicts with something but with what remains a mystery.

FYI: I myself run a Centos server with PHP 5.2.6 without any problems.
There's something wrong with your setup or something similar. 

Thank you for the input. This complicates the problem. Let?s do some differential diagnosis.

The problem is caused by: PHP configuration and/or Apache configuration and/or the code.

As expert you don?t see any problem with PHP configuration.
The code works in 2 other servers (with minor versions of PHP I should remark)
Apache is compiled (because of this very problem) without any tweaking because in my experience 99,99% of the problems occur because of a user?s error.
So IMHO it?s either Apache (but what in Apache?) or the code in this version of PHP. To exclude the second part, would you be so kind to provide me some code to type in the test page to see if it works in this particular version of PHP? Then if it won?t work it should be either Apache or a PHP bug.

Thank you.

P.S. I?ll be abroad (in Deutschland) for the next 8 days so please don?t expect my response soon.)

Just ditch Apache and start using something much better: Lighttpd + PHP as FastCGI. That's propably the difference here.

Oh! Oh! 
If this is the only way to correct the problem...

Is there any page with detailed info about installing it? I've found:
http://trac.lighttpd.net/trac/wiki/TutorialLighttpdAndPHP

I'll give it a try. Wish me luck

(Aristoteles wrote that luck helps only the prepared one).

This is definately not any PHP bug. It's just one of those Apache modules misbehaving, or some combination of them being incompatible.

We have resolved all issues for www.anavasis.gr

Thanks