PHP - Fiscal Year Calculations ! Please Help

I need to find the last Friday of each month and determine the start and end dates of each month based on the last Friday.  So, for September, the last Friday was the 27th, that means Saturday the 28th will be the last day of September.  September 29 will then start the first day of October....  October 25 is the last Friday in October, so Saturday October 26 will close out October.....  Sun Oct 27 starts November, etc...

7/28 - 8/31

9/1 - 9/28

9/29 - 10/26

10/27 - 11/30

I can build a table and manually key in the start and end dates then query as needed, but if there is a way to do it on the fly, I'd rather do it in php to eliminate mistakes.

Below is the code I'm currently using to find the first and last day of each calendar month, but I'll need to convert this to find the fiscal month based on the last Saturday of each month.  And go back a few years in the option select.

      <select name="dateselect" id="dateselect">


          <?php


          $today = date("Y-m-d");
          $monthbegin =   date("Y-m-d",strtotime('first day of this month', strtotime($today)));

          for( $i= 0 ; $i <= 52 ; $i++ )
          {
          if($i == 0){
          $monthselect = date('Y-m-d',strtotime($monthbegin));
          $monthdisplay = date('F Y',strtotime($monthbegin));
          echo '<option ' . ($i == 0 ? 'selected=\'selected\'' : '') . ' value="' . $monthselect . '" >' . $monthdisplay . '</option>';
          }
          else{
          $monthselect = date('Y-m-d',strtotime('-'."$i".' months',strtotime($monthbegin)));
          $monthdisplay = date('F Y',strtotime('-'."$i".' months',strtotime($monthbegin)));
          echo '<option ' . ($i == 0 ? 'selected=\'selected\'' : '') . ' value="' . $monthselect . '" >' . $monthdisplay . '</option>';

          }




          }
          ?>
          </select>

  $begin_date = $_GET["dateselect"];
  $end_date = date("Y-m-t", strtotime($begin_date));

<?php
class elo {
function get_rating($current_rating, $expected, $win = true)
{
if ($win === true)
{
$r = $current_rating;
$add = 32;
$multiplier = 1 - $expected;
$add = $add*$multiplier;
$r = $current_rating + $add;
return round($r,0);
}
else
{
$r = $current_rating;
$add = 32;
$multiplier = 0 - $expected;
$add = $add*$multiplier;
$r = $current_rating + $add;
return round($r,0);
}
}

function get_expected($player1_rating, $player2_rating)
{
$e = 1;
$divider = 1;
$power_of = $player2_rating - $player1_rating;
$power_of = $power_of / 400;
$power_of = 10^($power_of);
$divider = $divider + $power_of;
$e = $e/$divider;
return round($e,2);
}
}

$elo = new elo();
$a = 1000;
$b = 1000;
$chance['a'] = $elo->get_expected($a,$b);
$chance['b'] = $elo->get_expected($b,$a);
$chance['%a'] = $chance['a'] * 100;
$chance['%b'] = $chance['b'] * 100;
echo "Player A ({$a}) has a " . $chance['%a'] . "% Chance of winning.<br/>"; //should be 50% (0.5)
echo "Player B ({$b}) has a " . $chance['%b'] . "% chance of winning.<br/>"; //should be 50% (0.5)
$winpoints['a'] = $elo->get_rating($a, $chance['a']); //should return 1016
$winpoints['b'] = $elo->get_rating($b, $chance['b']); //should return 1016
echo "Player A's new rating will be {$winpoints['a']} if they win.<br/>";
echo "Player B's new rating will be {$winpoints['b']} if they win.<br/>";
$losspoints['a'] = $elo->get_rating($a, $chance['a'], false); //should return 984
$losspoints['b'] = $elo->get_rating($b, $chance['b'], false); //should return 984
echo "Player A's new rating will be {$losspoints['a']} if they lose.<br/>";
echo "Player B's new rating will be {$losspoints['b']} if they lose.<br/>";

//Parse Lake Ray Hubbard XML Data
$site = simplexml_load_file($LRH_data);{

        $LRH_bankfull   = '435.5';
        $LRH_totalDepth = '40';
        $LRH_current    = $site->observed->datum[0]->primary;
        $LRH_vaild      = $site->observed->datum[0]->valid;
        $LRH_updated    = DATE("D, M d, g:i a", STRTOTIME($LRH_vaild));

}

//Lets calculate the lake depatures from full pool for Lake Ray Hubbard
function LRH_calcLevel($LRH_current, $LRH_bankfull)
{
    //Get float values from strings
    $LRH_current = floatval($LRH_current);
    $LRH_bankfull = floatval($LRH_bankfull);
    //Calculate the difference
    $LRH_calcLevel = $LRH_current - $LRH_bankfull;
    //Format difference to two decimal places and add 'Ft'
    $LRH_calcLevelStr = (string) number_format($LRH_calcLevel, 2) . ' Ft';
    //If vlaue is positive add a + to beginning
    if($LRH_calcLevel>0) { $LRH_calcLevelStr = '+'.$LRH_calcLevelStr; }
    //Return the calculated formatted value
    return $LRH_calcLevelStr;
}

////Lets calculate the lake percentage from full pool for Lake Ray Hubbard
$val1 = $LRH_current;
$val2 = $LRH_bankfull;

$LRH_prec = ( $val1 / $val2) * 100;

// 1 digit after the decimal point
$LRH_prec = round($LRH_prec, 1);

//Lets convert the depature from full pool for Lake Ray Hubbard
function LRH_calcDepth($LRH_calcLevelStr, $LRH_totalDepth)
{
    //Get float values from strings
    $LRH_calcDepthStr = floatval($LRH_calcLevelStr);
    $LRH_totalDepth = floatval($LRH_totalDepth);
    //Calculate the difference
    $LRH_calcDepth = $LRH_calcDepthStr - $LRH_totalDepth;
    //Format difference to two decimal places and add 'Ft'
    $LRH_calcDepthStr = (string) number_format($LRH_calcDepth, 2) . ' Ft';
    //If vlaue is positive add a + to beginning
    if($LRH_calcDepth>0) { $LRH_calcDepthStr = '+'.$LRH_calcDepthStr; }
    //Return the calculated formatted value
    return $LRH_calcDepthStr;
}

////Lets calculate the lake percentage from full pool for Lake Ray Hubbard
$val1 = LRH_calcLevel($LRH_current, $LRH_bankfull);
$val2 = $LRH_totalDepth;