<?php
$sbc = sybase_connect($host, $user, $passwd);
sybase_select_db($db);

$sbr = sybase_query("select count(*) from head");
if($sbr) {
  $row = sybase_fetch_array($sbr);
  echo $row[0];
} else {
  echo "BUMMER";
}
?>

./configure  |\
  --with-apxs=/home/httpd/bin/apxs |\
  --with-sybase=/opt/sybase
Gives me the expected result.

./configure  |\
  --with-apxs=/home/httpd/bin/apxs |\
  --with-sybase=/opt/sybase --with-imap
Gives me:
  Warning: Sybase: A link to the server could not be established in 
  /home/runesk/public_html/foobar/sybase.php on line 3

The foloowing libs are used:
Sybase: Sybase DB-Library/10.0.4/P/Linux Intel/Linux 2.0.36 i586/1/Thu Sep 10 13:35:34 CEST 
imap  : imap-4.7-5.src.rpm