Array Reference

I want to compare dates in sequential records (in mysql format YYYY-MM-DD) extracted into an array. I have a loop to iterate through a set of records. In this loop, how can I refer to the previous record in the loop?

As in:

for ($i=0; $i <$num_results; i++) {
$row = mysql_fetch_assoc($result);
if ($row('thisDate') != the previous record's date) {
do something
}
}

This is related to PEAR how? This belongs in PHP Coding.

place the previous records date in a holding variable.