改变循环索引

对于同一个数组，我有一个内循环，但是在内循环中我删除了一些元素，新数组被分配给主数组，但是问题发生了，主循环索引仍然不变!

foreach ($newsletters as $index=>$mainNewsletterObj) {
    // var_dump($newsletters); // it prints new DATA !
         // the problem is here !
    echo 'up index is '.$index .'<br/>';  // it prints old index!!!!!!!!!!
      // make a copy of main array
      $newslettersArray = $newsletters; 
        //inner loop
     foreach ($newslettersArray as $key => $newsletterObj) {
    if ($newsletterObj['month'] == 3 );
         unset($newslettersArray[$key]);  //remove element
      } else
      {
     // make a new array of modified one to start index from 0
     $newslettersArray1 = array_values($newslettersArray); // to start index from 0
      // assign new modified array to the original one
     $newsletters = $newslettersArray1;
  }
}   // end inner loop
$index=0;
  echo 'down index is '.$index .'<br/>';  // it prints 0
 }  // end of outer loop