Reference number which automatically resets every month - php

Question

I am generating reference no REF-082013-001 (REF-mmyyyy-001) and incrementing the last part for every entry. REF-082013-001 for first record and REF-082013-002 for second and so on.
My Question is How can i reset the last number by php for every new month. Let say September 2013 I want it to be REF-09-2013-001 and auto increment it till the end of September and then in November reset it again.
Is there a ways to do this in php. Your help is much appreciated. Thank you
Update
Currently 'REF-'.date('m-Y').$maxnumberfromdb in single column called reference_no and Now thinking to store the mm-yyyy ref1 and last number in ref2 separately and start ref2 every first day of the month.

Answer 1

You can probably go with a single table, with an AUTO_INCREMENT field to handle the last part of the reference number, and a date/time field to track when it was last reset.
CREATE TABLE track_reference
ref_number INT(11) AUTO_INCREMENT,
last_reset DATETIME;
Then you write a function in PHP to get a new reference number, which (pseudo-code):
if (MONTH(time()) > MONTH(last_reset)) {
reset ref_number to 0 (use ALTER TABLE);
}
select (ref_number) into $variable;
return 'REF_<month><year>_$variable;
}
It's rough, but you get the idea. I'd also have YEAR appear before MONTH for making sorting by reference number easier later.

Answer 2

This is my code for reset counter and update last_reset, this is effective for me
<pre>
$date2 = new DateTime("now", new DateTimeZone('America/New_York') );
$month_end = strtotime('last day of this month', time());
$count = $data['sim_tarif_count'];
$date3=$date2->format('Y-m-d');
foreach ( $count as $r2 ){
$counts[] = $r2['count'];
$last_reset[] = $r2['last_reset'];}
$paddedNum = sprintf("%04d", $counts[0]);
$reg_id = 'SEQ'.$date2->format('Ymd').$paddedNum;
echo " ";
echo date('j', $month_end);
$counter = $counts[0]+1;
//for reset
if($date2->format('Y-m') > $last_reset[0])
{
$counter = 0;
$counting_update=$this->docs_model->update_time_counter($counter,$date3);
echo $counter = 0;
} else
{
$counting_update=$this->docs_model->update_time_count($counter);
}
</pre>