<?php
$one = array('start' => '2012-10-12', 'stop' => '2012-11-04', 'over' => true);
$two = array('start' => '2012-10-29', 'stop' => '2012-11-14', 'over' => false);
$three = array('start' => '2012-11-12', 'stop' => '2012-12-07', 'over' => false);
$arr = array($one, $two, $three);
$arr1 = $arr;

foreach($arr as $key=>$val)
    {
       if(isset($arr[$key+1]) && $arr[$key+1]['over'] == true)
       {
           $arr[$key]['stop'] = date('Y-m-d', strtotime($arr[$key+1]['start'] .' -1 day'));
           $arr[$key]['over'] = true;
       }
       if(isset($arr[$key-1]) && $arr[$key-1]['over'] == true)
       {
           $arr[$key]['start'] = date('Y-m-d', strtotime($arr[$key-1]['stop'] .' +1 day'));
           $arr[$key]['over'] = true;
       }
    }

foreach($arr1 as $key=>$val)
{
   $arr[$key]['over'] = $arr1[$key]['over'];
}
var_dump($arr);
?>

array(3) {
  [0]=>
  array(3) {
    ["start"]=>
    string(10) "2012-10-12"
    ["stop"]=>
    string(10) "2012-11-04"
    ["over"]=>
    bool(true)
  }
  [1]=>
  array(3) {
    ["start"]=>
    string(10) "2012-11-05"
    ["stop"]=>
    string(10) "2012-11-14"
    ["over"]=>
    bool(false)
  }
  [2]=>
  array(3) {
    ["start"]=>
    string(10) "2012-11-15"
    ["stop"]=>
    string(10) "2012-12-07"
    ["over"]=>
    bool(false)
  }
}