In PHP PDO(PHP Data Objects) tutorials I've been reading that the advantage of PDO over MySQLi is that PDO is platform independent. That said means you wrote a script with PHP PDO using MySQL database management system. Later you want to switch your web application to another Database Management System like Oracle, you will not need to rewrite your queries. While in case of MySQLi you had to rewrite your queries.
Now I'm confused by looking at the following line
$conn = new PDO("mysql:host=$servername;dbname=myDB", $username, $password);
Why do we need to mention the "mysql" in the first parameter? And if I've to port my website to another DBMS, would I not need to replace this "mysql" with something like "oracle"?
Hopefully somebody clarify this.
Thanks