If you go for a ODBC solution I'd go for the usual UnixODBC, which for
PHP5 is quite easy to include. I'd recommend *NOT* to use odbc.ini (mother
of all ODBC problems on linux) and instead include the parameter in the
actual obdc_connect();

$genODBC="Driver={Adaptive Server Anywhere 9.0};CommLinks=tcpip
{dobroadcast=no;host=83.133.64.XXX;ServerPort=5010};ServerName=Production;D
atabaseName=REXREX;ConnectionName=REXREX;uid=dba;pwd=blabla;
  $Q = "select Id from REX.MessageContext";

  print("<h1>Test ODBC</h1>");
  $AdmConnect = odbc_connect($genODBC,'','');
  $lres = odbc_exec($AdmConnect, $Q);
  while(odbc_fetch_row($lres)){
    return odbc_result($lres, 1);
  }
  odbc_close($lres);

Whether or not you ned the ServerPort/ClientPort parameters depends on
local firewall settings (good luck with that). Be sure to set parameters
on the serverside correspondingly.

I'm not sure whether this approach works with older Sybase versions. It
does work with PHP4.