Centos – Installing GDChart at CentOS fails: pecl/gdchart requires PHP extension “gd”

has anybody solved the problem of installing GDChart on CentOS 5.5 Linux
(I've tried both 32 and 64 bit versions)?

I have:

# rpm -qa | grep -i php
php-pear-1.4.9-6.el5
php-gd-5.1.6-27.el5
php-ldap-5.1.6-27.el5
php-pgsql-5.1.6-27.el5
php-5.1.6-27.el5
php-pdo-5.1.6-27.el5
php-common-5.1.6-27.el5
php-cli-5.1.6-27.el5
php-devel-5.1.6-27.el5

And the "pecl" seems to find GDChart in its repository:

#  sudo pecl search GDChart
Retrieving data...0%....50%....Matched packages, channel pecl.php.net:
=======================================
Package Stable/(Latest)    Local
GDChart -n/a-/(0.2.0 beta)       GDChart Based Graphing Interface

But installing it fails:

# sudo pecl install GDChart
Failed to download pecl/GDChart within preferred state "stable",
latest release is version 0.2.0, stability "beta", use
"channel://pecl.php.net/GDChart-0.2.0" to install
Cannot initialize 'GDChart', invalid or missing package file
Package "GDChart" is not valid
install failed

Ok, then I try the suggested "URL":

# sudo pecl install "channel://pecl.php.net/GDChart-0.2.0"
pecl/gdchart requires PHP extension "gd"
No valid packages found
install failed

But I do have both "gd" and "php-gd" rpms installed and enabled:

# cat /etc/php.d/gd.ini
; Enable gd extension module
extension=gd.so

And phpinfo() shows "gd" as enabled too:

GD Support  enabled
GD Version  bundled (2.0.28 compatible)
FreeType Support  enabled
FreeType Linkage  with freetype
FreeType Version  2.2.1
GIF Read Support  enabled
GIF Create Support  enabled
JPG Support  enabled
PNG Support  enabled
WBMP Support  enabled
XBM Support  enabled 

Any suggestions please, except compiling it by hand?
Alex