Trying to connect to an external ODBC data source

I have a need to connect to a data source on an old unix box via ODBC, but I don’t seem to be getting far and I can’t find any examples to help me.

I have started with https://docs.joomla.org/Connecting_to_an_external_database and set up the following details:

$option['driver'] = 'pdo';            // Database driver name
$option['host'] = 'nnn.nnn.nnn.nnn:nnnn';    // Database host name
$options['dsn'] = 'Fred';
$option['user'] = 'Barney';       // User for database authentication
$option['password'] = 'Wilma';   // Password for database authentication
$option['database'] = 'dbname';      // Database name
$option['prefix'] = '';             // Database prefix (may be empty)

$dbx = JDatabaseDriver::getInstance($option);

With that configuration, I get an error message of:

Cannot instantiate abstract class JDatabaseDriverPdo
E:wwwbedrocklibrariesjoomladatabasedriver.php:313

This happens because driver.php takes the value ‘pdo’ from $option['driver'] = 'pdo'; and appends it to a class of JDatabaseDriver to be found in librariesdatabasedriverpdo.php which is an abstract class the extends JDatabaseDriver hence the message. It is the only abstract class in /driver. If I replace ‘pdo’ with ‘odbc’, I get a message to say it can’t load the database driver which will be because the class JDatabaseDriverOdbc is not found.

When I look at librariesdatabasedriverpdo.php, I can see that ‘odbc’ is the default if no other driver is specified and further down I can see the connection string set up for ‘odbc’ so it looks like it is supported.

public function __construct($options)
{
    // Get some basic values from the options.
    $options['driver'] = (isset($options['driver'])) ? $options['driver'] : 'odbc';
    $options['dsn'] = (isset($options['dsn'])) ? $options['dsn'] : '';
    $options['host'] = (isset($options['host'])) ? $options['host'] : 'localhost';
    ...
    // Find the correct PDO DSN Format to use:
    switch ($this->options['driver'])
    {
    ..
    case 'odbc':
    $format = 'odbc:DSN=#DSN#;UID:#USER#;PWD=#PASSWORD#';
    $replace = array('#DSN#', '#USER#', '#PASSWORD#');
    $with = array($this->options['dsn'], $this->options['user'], $this->options['password']);

It seems to me that $option['driver'] = has two different uses depending on where it is used, as either a suffix to build a class name or as a switch to set the connection string.

I have also tried to use the class directly with

`$option['driver'] = 'odbc';
...
$dbx = JDatabaseDriverPdo::getInstance($option);

however that still tries to find a class of JDatabaseDriverOdbc from driver.php

I really could use some pointers in the right direction or an example of ODBC in use.

Some hours later…

Looking at the code in driver.php and some of the data base formats in librariesdatabasedriver it would appear I need to create a new class that extends JDatabaseDriverPdo, eg. class JDatabaseDriverOdbc extends JDatabaseDriverPdo and make that available to my code. So I think the Joomla answer is yes you can do it if you write your own connector.

public function getQuery($new = false)
    {
        if ($new)
        {
            // Derive the class name from the driver.
            $class = 'JDatabaseQuery' . ucfirst($this->name);

            // Make sure we have a query class for this driver.
            if (!class_exists($class))
            {
                // If it doesn't exist we are at an impasse so throw an exception.
                throw new JDatabaseExceptionUnsupported('Database Query Class not found.');
            }

            return new $class($this);
        }
        else
        {
            return $this->sql;
        }
    }