<?php
if(isset($_POST)){
    print_r($_POST);
    #Array ( [id] => Array ( [0] => 3 [1] => 4 ) [del] => 删除 )
#也就是说，name中[]会被解析为0,1……
#$_POST['id'][0] => 3
}
?>

<form id="form3" name="form3" method="post" action="test18.php">
  <p>
  <label for="id2">删除序号为</label>
  <input name="id[]" type="text" id="id2" size="10" value="3" />
  <input name="id[]" type="text" id="id2" size="10" value="3" />
  的记录
  </p>
  <p>
  <input type="submit" name="del" id="del" value="删除" />
  </p>
</form>