gd for php5 under RH ES4

I am trying to use the php gd library (for imagecreate, etc) with php5 
under Red Hat ES4.  I tried installing php-gd via webmin (which in turn, 
I see, uses up2date), but get the following error in the apache error 
log when restarting:
PHP Warning:  PHP Startup: Unable to load dynamic library 
'/usr/lib/php4/gd.so' - /usr/lib/php4/gd.so: undefined symbol: 
empty_string in Unknown on line 0

I don't know if the problem is that php-gd is a php4 library or there is 
something else that I need to install or do.  I saw something about 
php5-gd, but webmin/up2date can't find anything by this name.

I have searched for a bit on this without joy; any guidance is 
appreciated.  I am not a system administrator by training, but am a 
longtime Unix programmer, so I can handle reasonably low level 
instructions, if necessary.  I did post this to a Red Hat list without 
any reply so far.

Thanks in advance,
Doug