Why PDO constructor does not accept host, dbname, database type, etc. As arguments to a regular function?

Question

I am learning PDO, and the constructor seems to use an unorthodox and inconsistent way of accepting arguments. Namely:

$dbh = new PDO("mysql:host=$host;dbname=$dbname", $user, $pass); 

Why is it different from the usual format:

 $dbh = new PDO("mysql", $host, $dbname, $user, $pass); 

Or, since the first two arguments (host and dbname) are written as one long string, why not continue with the other two arguments? Namely:

 $dbh = new PDO("mysql:host=$host;dbname=$dbname;user=$user;pass=$pass"); 

Answer 1

The DSN describes where the data source is and how to connect to it. User and password are authentication parameters that do not affect access to the data source.

Having a user and a pass in the DSN will look like you have to enter your username and password in the URL of the website you are going to.

Answer 2

PDO uses DSN to connect, username and password are optional parameters for DSN string.

check out http://www.php.net/manual/en/pdo.construct.php

I really don't think this is “unorthodox or inconsistent," ODBC in PHP uses the same process.