There is a third required argument to this function, if you pass just the 2 listed here the function will return no data.
The third argument is the number of results you want, if you want everything simply pass count($OPTSARRAY) as arg3.
$opts = array ( "AVERAGE", "--start", '-1d');
print_r(rrd_fetch('./rrds/file.rrd', $opts, count($opts)));
(PECL rrd >= 0.9.0)
rrd_fetch — Fetch the data for graph as array.
Gets data for graph output from RRD database file as array. This function has same result as rrd_graph(), but fetched data are returned as array, no image file is created.
RRD database file name.
Array of options for resolution specification.
Returns information about retrieved graph data.