php-rrdtool bug

lagi asyik ngoprek rrdtool. tapi pas mo integrasi dengan php, ketemu bug. di log apache ada pesan: PHP Warning: Unknown(): Invalid library (maybe not a PHP library) 'rrdtool.so' in Unknown on line 0 after searching for a while in google, dapet informasi menarik di: http://www.ee.ethz.ch/~slist/rrd-users/msg06224.html