problem about php program

[bpam]

My php programer and I designed a php program which include a form to keyin our business data.
We want to keep the values on the text area while we submit the form with some errors, the form goes back.

Here are our php program below.

PHP Code:

<?
ob_start();
session_cache_limiter("must-revalidate");
?>
<form action="test_write.php" method="post" encType="multipart/form-data" name="frm">
  <label>A：
  <input type="text" name="test1" id="test1">
  </label>
  <p>
    <label>B：
    <input type="text" name="test2" id="test2">
    </label>
  </p>
  <p>
    <label>
    <input type="submit" name="submit" id="submit" value="Out">
    </label>
  </p>
</form>

But, the setting ob_start(); not works.
The php session is ok, but the values of input text are gone.

What should I do to fix this problem?
Should I modify my php.ini?

[bpam]

Oh! finally, I know the answer.
Modify this in php.ini,

PHP Code:

session.cache_limiter = must-revalidate 


The problem answered.