function ServerInfo()
 {
     if (!empty($this->host) && ADODB_PHPVER >= 0x4300) {
         $dsn = strtoupper($this->host);
         $first = true;
         $found = false;
         while (true) {
             $rez = odbc_data_source($this->_connectionID, $first ? SQL_FETCH_FIRST : SQL_FETCH_NEXT);
             $first = false;
             if (!is_array($rez)) {
                 break;
             }
             if (strtoupper($rez['server']) == $dsn) {
                 $found = true;
                 break;
             }
         }
         if (!$found) {
             return ADOConnection::ServerInfo();
         }
         if (!isset($rez['version'])) {
             $rez['version'] = '';
         }
         return $rez;
     } else {
         return ADOConnection::ServerInfo();
     }
 }

 /**
  * Obtains the query string needed for listing a given type of objects
  *
  * Thanks to [email protected] and [email protected].
  *
  * @param string $type  the kind of objects you want to retrieve
  *
  * @return string  the list of objects requested
  *
  * @access protected
  * @see DB_common::getListOf()
  * @since Method available since Release 1.7.0
  */
 function getSpecialQuery($type)
 {
     switch ($type) {
         case 'databases':
             if (!function_exists('odbc_data_source')) {
                 return null;
             }
             $res = @odbc_data_source($this->connection, SQL_FETCH_FIRST);
             if (is_array($res)) {
                 $out = array($res['server']);
                 while ($res = @odbc_data_source($this->connection, SQL_FETCH_NEXT)) {
                     $out[] = $res['server'];
                 }
                 return $out;
             } else {
                 return $this->odbcRaiseError();
             }
             break;
         case 'tables':
         case 'schema.tables':
             $keep = 'TABLE';
             break;
         case 'views':
             $keep = 'VIEW';
             break;
         default:
             return null;
     }
     /*
      * Removing non-conforming items in the while loop rather than
      * in the odbc_tables() call because some backends choke on this:
      *     odbc_tables($this->connection, '', '', '', 'TABLE')
      */
     $res = @odbc_tables($this->connection);
     if (!$res) {
         return $this->odbcRaiseError();
     }
     $out = array();
     while ($row = odbc_fetch_array($res)) {
         if ($row['TABLE_TYPE'] != $keep) {
             continue;
         }
         if ($type == 'schema.tables') {
             $out[] = $row['TABLE_SCHEM'] . '.' . $row['TABLE_NAME'];
         } else {
             $out[] = $row['TABLE_NAME'];
         }
     }
     return $out;
 }

<?php

include 'config.inc';
$conn = odbc_connect($dsn, $user, $pass);
var_dump(odbc_data_source($conn, NULL));
var_dump(odbc_data_source($conn, ''));
var_dump(odbc_data_source($conn, SQL_FETCH_FIRST));