In WHM when you attempt to build PHP + GD, it may look for libXpm. You will see something like "configure: error: libXpm.(a|so) not found." in the output.

The solution is to install the xorg-x11-devel package, which includes the necessary libs. If you have Fedora Core 2, you can read about Setting up Yum on FC2 which will allow you to easily download and install the package. For other operating systems, you will need to obtain the package for xorg-x11-devel and install it by hand.

Code:
root@server [/]# yum install xorg-x11-devel
Gathering header information file(s) from server(s)
Server: Fedora Core 2 - i386 - Base
Server: Fedora Core 2 - i386 - Released Updates
Finding updated packages
Downloading needed headers
Resolving dependencies
.Dependencies resolved
I will do the following:
[install: xorg-x11-devel 6.7.0-14.i386]
I will install/upgrade these to satisfy the dependencies:
[deps: fontconfig-devel 2.2.1-10.i386]
Is this ok [y/N]: y
Downloading Packages
Getting xorg-x11-devel-6.7.0-14.i386.rpm
xorg-x11-devel-6.7.0-14.i 100% |=========================| 5.1 MB    00:03
Getting fontconfig-devel-2.2.1-10.i386.rpm
fontconfig-devel-2.2.1-10 100% |=========================| 236 kB    00:00
Running test transaction:
/etc/security/selinux/file_contexts: No such file or directory
Test transaction complete, Success!
/etc/security/selinux/file_contexts: No such file or directory
fontconfig-devel 100 % done 1/2
xorg-x11-devel 100 % done 2/2
Installed:  xorg-x11-devel 6.7.0-14.i386
Dep Installed:  fontconfig-devel 2.2.1-10.i386
Transaction(s) Complete
root@server [/]#

root@server [/]# ls -l /usr/X11R6/lib | grep -i xpm
-rw-r--r--  1 root root   87424 Mar 24  2005 libXpm.a
lrwxrwxrwx  1 root root      14 Jan 21 15:04 libXpm.so -> libXpm.so.4.11*
lrwxrwxrwx  1 root root      14 Jan 20 21:41 libXpm.so.4 -> libXpm.so.4.11*
-rwxr-xr-x  1 root root   59616 Mar 24  2005 libXpm.so.4.11*
Then, attempt to rebuild apache again.