rrdtool - PHP Fatal error: Call to undefined function rrd_info() -

i installed rrdtool php on centos yum install php-rrdtool.

i can run php -m , can see rrdtool listed in output. rrdtool support loaded, however, when try use of rrdtool functions in php, fails following message:

php fatal error:  call undefined function rrd_info() php fatal error:  call undefined function rrd_xport() 

it looks hasn't been loaded...

what doing wrong? seems ok me...