The given testcase has an extra semi-colon in the second query.  The new testcase below shows that the initial connection is getting associated with the second user.

Testcase:

<?php
  function qry(&$c, $s) {
      echo "===&gt;BEGIN<br>";
      $rSth = OCIParse($c, $s);
      $rRet = OCIExecute($rSth);
      echo "<br>";
      while ($succ = OCIFetchInto($rSth, $row)) {
        foreach ($row as $item) {
          echo ($item?htmlentities($item):'&nbsp;')." ";
        }
        echo "<br>\n";
      }
      echo "===&gt;CLOSE<br><br>";
      ocifreestatement($rSth);
  }

  $statement1 = "select user from dual";

  echo "===&gt;OCINLogin #1: Connect as SCOTT<br>";
  $c1 = OCINlogon('scott', 'tiger', 'F10D' );

  echo "===&gt;Query first connection<br>";
  qry($c1, $statement1);

  echo "===&gt;OCINLogin #2: Connect as HR<br>";
  $c2 = OCINlogon('hr', 'hr', 'F10D');

  echo "===&gt;Re-query first connection<br>";
  qry($c1, $statement1);

?>

Actual Output:

===>OCINLogin #1: Connect as SCOTT
===>Query first connection
===>BEGIN

SCOTT
===>CLOSE

===>OCINLogin #2: Connect as HR
===>Re-query first connection
===>BEGIN

HR
===>CLOSE


Expected output is similar with the usernames in this order: SCOTT, SCOTT

Chris, is it important to have different users in your example?
Tested under 1 user (but using ociNlogin();) and it works fine.

The "business requirement" comes from the original report in
http://forums.oracle.com/forums/thread.jsp?forum=178&thread=251141

I don't think the way $c1 is impacted by the second login is obvious
or nice behavior.

I feel the problem is related to some of the common OCI8 connection
issues due to the caching and reuse of handles.  It would be nice to
resolve these issues.

There is no Oracle-OCI reason why two users can't be connected at one
time.  I think it should be allowed in PHP.  But if you think the
PHP-OCI8 interface should not support concurrent connections, can a
PHP error be generated at the time of the second OCINLogin()?

No, of course you should able to connect to Oracle from PHP using different logins. 
My question should be read in this way: "are you able to reproduce it under 1 user, but with different connections, because I was too lazy to create a new user in Oracle?".
Btw, I've already created additional user and tested your code - your example works perfectly for me.

Using one user would make it harder to demonstrate the 
problem. Sorry I didn't include create user scripts etc.

I retested with 4.3.10-dev and 5.0.3-dev binaries of a few 
minutes ago. I am using W2K with Oracle 9.2 client libraries.
I am still seeing the usernames printed as SCOTT and HR, 
which is "incorrect".

I can see the problem now. 
Will look at it closer a bit later..

Hy

I'm having the following problem:

Warning: ociexecute(): OCIStmtExecute: ORA-03106: fatal two-task communication protocol error in /var/www/html/helpdesk/migracao/view.php on line 10

Warning: ocifetchinto(): OCIFetchInto: ORA-24374: define not done before fetch or execute and fetch in /var/www/html/helpdesk/migracao/view.php on line 12

These errors are in a simple query. Is it about the bug on php?

thank's

On my system, I noticed that the appearance of the bug depends on the way of starting my .php file.
If I start the script from bash, it works okay.
If I start the script directly from cron, it produces the error described here.
So, I solved my problem starting it from cron with such a string:
"su - user -c "/path/to/script.php"

The bug has been fixed in OCI8 v.1.1, which is available in CVS HEAD and PECL (use `pear install oci8-beta` to install it).