Whenever a GET/POST is done from a web form, the resulting $_GET, $_POST arrays are auto-generated with the first 4 chars of the string cut-off IF the string is 4 or more chars.

For instance:

<form method="get">
name: <input type="text" name="test[name]"><br>
age: <input type="text" name="test[age]"><br>
<input type="submit">
</form>

completed with name = "123456"
and age = "654321"

would generate:

(with this code)
<pre>
<?=print_r($_GET)?>
</pre>

the following:

Array
(
    [0] => 56
    [1] => 21
)

as you can see the first 4 chars have been truncated.

it's been done with linux slackware 8.1, kernel 2.4.19+grsecurity on AMD and Intel microprocessors.

the configure line:

#!/bin/sh

./configure \
--prefix=/usr/local/php \
--enable-force-cgi-redirect \
--with-zlib \
--enable-sockets \
--with-mysql=/usr/local/mysql \
--enable-memory-limit \
--with-mm=/root/software/apache/mm-1.1.3/ \
--with-gd=/usr/local/gd-lib \
--enable-ftp \
--enable-calendar \
--with-jpeg-dir=/usr \
--with-png-dir=/usr \
--with-freetype-dir= \
--enable-gd-native-ttf \
--with-mcrypt=/usr/local/lib/libmcrypt \
--enable-inline-optimization \
--enable-pcntl \
--enable-mbstring \
--enable-mbstr-enc-trans \
--enable-mbregex \
--with-imap=/root/software/lib/imap-2002/ \
--with-imap-ssl \
--with-openssl

with version 4.2.3. have not tested any variants.