php与js互相调用

1 <?php 
2 echo ‘<script>var yearid=$("#yearId").val()</script>‘;
3 echo $yearid=‘<script>document.write(yearid);</script>‘;
4 ?>

1 <?php
2 $userId=100;
3 ?>
4  <script>
5 var userId;
6 userId=$("#userId").value;
7 alert (userId);
8 </script>
9 <input type="text" name="userId" id="userId" value="<?php echo $userId; ?>">