(PHP 5 >= 5.1.3, PECL pdo >= 1.0.3)
PDO::getAvailableDrivers — Return an array of available PDO drivers
   This function returns all currently available PDO drivers which can be used
   in DSN parameter of
   PDO::__construct().
  
PDO::getAvailableDrivers() returns an array of PDO driver names. If no drivers are available, it returns an empty array.
Example #1 A PDO::getAvailableDrivers() example
<?php
print_r(PDO::getAvailableDrivers());
?>
The above example will output something similar to:
Array
(
    [0] => mysql
    [1] => sqlite
)