$arr =  array('comment', 'comment1',
    'comment2', 'comment3',
    'comment4', 'comment5',
    'comment6', 'comment7'
);

foreach ($arr as $key=>$value) {

    if ($key < (count($arr)/2)) {

        echo $arr[$key*2].'  ';
        echo $arr[($key*2)+1].'<br/>';

    }

}

print_r($arr);

//comment comment1
//comment2 comment3
//comment4 comment5
//comment6 comment7

$array = array('Вася','Петя','Коля','Джон','Гарик');


foreach($array as $k=>$v){
  echo 'Было: ';
  echo $v;
  echo ' <-> ';
  echo 'Стало: ';
  echo $array[$k+1];
  echo '<br />';

}