Yet Another "session_start() Cannot send session cache limiter - headers already sent" Que...

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I'm somewhat of a newbie to PHP coding, but have developed a site
using the technology, and have been pleasantly surprised by the
capabilities offered.  I am more comfortable in the ASP world, however
and am really struggling with managing sessions in PHP, based on my
experiences with managing sessions in ASP.

99.9% of the feedback I have seen when dealing with the errors has
referred to having whitespace before the <?php or after the ?>.  I
have opened my source in several different editors and can't find that
to be the case with my code.  Aside from having general issues with
the basic methodology in which I am managing sessions, I am completely
perplexed as to why I am getting these errors, from time to time...

For those who might have recommendations on an overall session
management strategy, I basically want to allow my user to come into my
site, through any page that might be bookmarked.  Not all pages are
going to require a session, but they may be required to have a session
value set in order to perform certain administrative functions (which
requires a successful login), so I would need to check for the
existence of a session value and log them in and set it, if it doesn't

Now to my specific problem...

I have an include page called master_session.php, which looks like
this (no whitespaces before or after php tags):
  if (! isset($ADMIN_session)) {

I have a login page, which looks like this (no whitespace before the
include of master_session)
<?php require_once($_SERVER['DOCUMENT_ROOT'].'/common/includes/
master_session.php'); ?>
<?php if ($content_identifier == false){
$content_identifier = 'parish';}?>
<? $page_title = "Administration"; ?>
<?php require_once($_SERVER['DOCUMENT_ROOT'].'/common/includes/
master_header.php'); ?>
<?php require_once($_SERVER['DOCUMENT_ROOT'].'/common/includes/
master_nav.php'); ?>
<?php require_once($_SERVER['DOCUMENT_ROOT'].'/common/includes/
bg100.php'); ?>
<form name="criteria_form" action="adminvalidation.php" method="post">
      <table height="100%" border="0" width="81%" align="center"
          <td colspan="2" height="40">&nbsp;</td>
        <? if ($ == "invalid")
            echo "The username/password you have entered is invalid, or you do
not have privileges to perform administrative functions.  If you feel
you've received this message in error, please contact your system
          <td colspan="2" align="center"><strong>Please Login</strong></
          <td colspan="2" height="40">&nbsp;</td>
          <td align="right">Username&nbsp;</td>
          <td><input type="text" name="user_nm" size="8" maxlength="8">
          <td align="right">Password&nbsp;</td>
          <td><input type="password" name="password" size="10"
          <td colspan="2" height="40">&nbsp;</td>
          <td colspan="2" align="center"><input type="submit"
name="Submit" value="Submit">
            <td><input type="hidden" name="content_identifier" value="<?echo
<?php require_once($_SERVER['DOCUMENT_ROOT'].'/common/includes/
master_footer.php'); ?>

master_header.php is where my HTML code starts:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">


Is there anything in here that jumps out at anyone, as to why I'm
getting the error?  The exact error is:

Warning: session_start() [function.session-start]: Cannot send session
cache limiter - headers already sent (output started at /home/holytrin/
public_html/common/admin/admin.php:2) in /home/holytrin/public_html/
common/includes/master_session.php on line 4

btw..  I do an ob_end_flush() in the master_footer.php file, on the
very last line...

Any help would be greatly appreciated!!!

Best Regards,

Re: Yet Another "session_start() Cannot send session cache limiter - headers already sent" Question

three-eight-hotel wrote:

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Hi Todd,

You're more likely to get sensible answers to your questions if you try to
keep to the point - read this:

From what you've posted the most likely causes of the problem are:

1) the BOM marker at the start of a UTF-8 encoded source file - you *must*
save your files as ASCII.

2) an auto-prepend file specified in the php.ini or webserver config.



Re: Yet Another "session_start() Cannot send session cache limiter - headers already sent" Question

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the essential problem is one of sending a header, response headers
have to be sent before any response body, so whenever you call any
function before session_start() which sends a header, you might have
trouble if the function returns output.
calling session_start first will fix this of course, and it doesnt
affect the use of ob_start() since that is about buffering response
body output.

what you are doing is saying when you call ob_start is "everything
after this point should be captured and stored in the buffer", but
what you then output is a header, something which can be sent first,
and should not be captured.

Re: Yet Another "session_start() Cannot send session cache limiter - headers already sent" Question

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btw, am I to assume you are using ob_start being you are implementing
some kind of compression - if not, then don't bother using it.
Also convert all short tags <? to <?php which is the standard these
days, and will make your scripts easier to port onwards, and when you
finally turn off short tags in the php.ini (or upgrade) you will be
able to use <?xml style declarations without conflicts.
Also I assume you understand about turning globals off, it's just that
if you don't asking questions like
if( $content_identifier == false )
can get you into trouble because later you print that value out (which
you set to parish but could be overridden to something nasty) in the
markup un-filtered.
I should say that I am not in full possession of the facts so it isn't
intended as a -ve critique, more an observation based on what I can

Re: Yet Another "session_start() Cannot send session cache limiter - headers already sent" Question

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Hi.  I've been having the same problem and I just figured it out.  You
can't have anything come before the session call (session_start()).
You can't even have a blank line before the "<?php" tag.  That's what
happened to me.  The session call worked fine on all but one of my
pages.  I put session_start() at the very top of my header.php file (<?
php session_start(); ?>), which is on the very first line of each of
my pages (<?php include ('includes/header.php');).  However, on one of
my pages, the code looked like this (I added the line numbers to
emphasize the point):

   2. <?php include ('includes/header.php');
   3.  $page_title = 'Title';

 I know it sounds stupid, but the problem was that empty line of code
before my <?php tag.  I deleted the first line so the code looked like

   1. <?php include ('includes/header.php');
   2.  $page_title = 'Title';

And it works fine.

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