I've got code that that uses dba_open() with the db3
handler and works with php4.1.2 on apache 1.3.19; yet the
same code fails with php4.1.2 and apache 1.3.26. 

  if(extension_loaded("dba")) {
    echo "okay  - dba extension loaded<br>\n";

    if(strlen($DB)) { # set in httpd.conf
      $dbtype = $DB;
      echo "okay        - db is $DB<br>\n";
    } else {
      $dbtype = "db2";
      echo "okay        - using db2<br>\n";
    }
    $dbfile = "/usr/local/httpd/search/test-tuidb";    # info by tui
    if(file_exists($dbfile)) {
      echo "okay  - tuidb file $dbfile found<br>\n";
      $id = dba_open($dbfile, "r", $dbtype);
      if ($id) {
        echo "okay  - open worked<br>\n";
        $key = "tui";
        if(dba_exists($key, $id)) {
          $keys = dba_fetch($key, $id);
          echo "okay  - 'tui' entry is $keys<br>\n";
        } else {
          echo "bad  - no 'tui' entry found<br>\n";
        }

      } else {
        echo "bad  - open failed; ";
        echo "PHP error message: $php_errormsg<br>\n";
      }
    } else {
      echo "bad   - tuidb file not found<br>\n";
    }

  } // if dba extension loaded
  else {
    echo "bad   - no dba extension<br>\n";
  }

On the working machine: 
okay	- dba extension loaded<br>
okay	- db is db3<br>
okay  - tuidb file /usr/local/httpd/search/test-tuidb found<br>
okay  - open worked<br>
okay  - 'tui' entry is YES OH YES

On the non-working machine:okay	- dba extension loaded<br>
okay	- db is db3<br>
okay  - tuidb file /usr/local/httpd/search/test-tuidb found<br>
<br>
<b>Warning</b>:  driver initialization failed in <b>/usr/local/httpd/html/winamp/testit.html</b> on line <b>23</b><br>
bad  - open failed; PHP error message: <br>


On both machines PHP was built with the same config options,
apache was built with the same config options, the apache
config files are largely the same (hostname and IP are
changed), php conf files are identical. If I swap binaries
and leave all the conf and html files as is, I can duplicate
either situation on either machine.

Here's how I configured PHP:
'./configure' \
'--with-db3' \
'--with-apxs=/usr/sbin/apxs' \
'--with-mysql=/usr/' \
'--enable-bcmath' \
'--with-config-file-path=/etc/httpd/conf' \
"$@"

Here's how I configured Apache:
./configure \
"--with-layout=Mine" \
"--enable-module=all" \
"--enable-shared=max" \
"--with-perl=/usr/bin/perl" \
"$@"

For kicks I just built PHP 4.2.1: same broken behaviour.

It sure looks like something in the new apache is breaking
this, but what? Why?

Have experienced the same problem on Linux.

With two i386 machines, here were our findings:

Machine that fails
------------------
- Red Hat 7.2 base
- Apache: 1.3.26 compiled from source
- PHP: 4.2.1 compiled from source using (amongst others) --with-db3

Machine that works
------------------
- Red Hat 7.3 base
- Apache: 1.3.23-14 (Red Hat binary RPM)
- PHP: 4.2.1 compiled from source using (amongst others) --with-db3

Further to my above comment, it also does the same thing with --with-db2.

Sorry, but the bug system is not the appropriate forum for asking
support questions. Your problem does not imply a bug in PHP itself.
For a list of more appropriate places to ask for help using PHP,
please visit http://www.php.net/support.php

Thank you for your interest in PHP.

I can only replicate this if I don't have the path right.

Please check that you're creating the correct path to an existing directory.

This confused me too, but "sfox" resolute(?) reply made me look again. The problem is not only with incorrect paths, but appears also when the file exists and has a non-db3 format.