some problem with cacti graph
 

i have insatalled cacti-0.8.7d onto my ubuntu-8.04.i installed it in /opt/lampp/htdocs/ directory by using xampp (it comes with mysql,php,apache) installation method(go to site http://www.in2dwok.com/indawok/?page_id=18).but im getting empty rra file and also im getting following errors if i try to plot cacti graph----
[1]when i run php /opt/lampp/htdocs/cacti/poller.phpPHP then im getting----->
Warning: PHP Startup: Unable to load dynamic library '/usr/lib/php5/20060613/msql.so' - /usr/lib/php5/20060613/msql.so: cannot open shared object file: No such file or directory in Unknown on line 0
FATAL: Cannot connect to MySQL server on 'localhost'. Please make sure you have specified a valid MySQL database name in 'include/config.php'
[2]when i try to create graph by using cacti window (http://localhost/cacti)then im getting----->

RRDTool Command:
/usr/bin/rrdtool graph - \
--imgformat=PNG \
--start=-86400 \
--end=-300 \
--title="localhost - Traffic" \
--rigid \
--base=1000 \
--height=120 \
--width=500 \
--alt-autoscale-max \
--lower-limit=0 \
--vertical-label="bits per second" \
--slope-mode \
--font TITLE:12: \
--font AXIS:8: \
--font LEGEND:10: \
--font UNIT:8: \
CDEF:cdefa=a,8,* \
CDEF:cdefe=a,8,* \
AREA:cdefa#00CF00FF:"Inbound" \
GPRINT:cdefa:LAST:" Current\:%8.2lf %s" \
GPRINT:cdefa:AVERAGE:"Average\:%8.2lf %s" \
GPRINT:cdefa:MAX:"Maximum\:%8.2lf %s\n" \
LINE1:cdefe#002A97FF:"Outbound" \
GPRINT:cdefe:LAST:"Current\:%8.2lf %s" \
GPRINT:cdefe:AVERAGE:"Average\:%8.2lf %s" \
GPRINT:cdefe:MAX:"Maximum\:%8.2lf %s\n"

RRDTool Says:
ERROR: invalid rpn expression in: a,8,*
>>>> when i search on the net then i come to know that-- DEF or CDEF "a" does not exist, thus "a" is not a valid number or variable, thus the expression is invalid.
but the problem is if DEF or CDEF "a" does not exist then how to get them exist...
plz give me proper solution and it will be better if u provide me step by step method right from the 'adding of devices' to 'plotting of graph' in cacti.
thanks alot....

Does this question go along with the other Cacti/graphing questions you posted too??