PDOdsn

PDOdsn is a term used in some documentation to refer to the DSN (data source name) string used by the PHP Data Objects (PDO) extension to establish a database connection. The DSN encodes the driver and connection parameters, and is supplied to the PDO constructor along with a username and password or with authentication handled by the driver.

Structure and purpose: A DSN begins with the driver name followed by a colon, then a series of key=value pairs separated by semicolons. Pairs are driver-specific, but common parameters include host, dbname, and charset for certain drivers. The DSN tells PDO which driver to use and which database or file to connect to, while authentication details are typically provided separately.

Examples: For MySQL, a DSN looks like "mysql:host=localhost;dbname=testdb;charset=utf8mb4". For PostgreSQL, "pgsql:host=localhost;port=5432;dbname=mydb". For SQLite, "sqlite:/absolute/path/to/database.db". For SQL Server, "sqlsrv:Server=localhost;Database=mydb".

Usage notes: To open a connection, you typically instantiate PDO with the DSN and credentials, for example new PDO($dsn, $user, $password). Credentials are often not embedded in the DSN itself unless the driver supports it; many drivers require passing username and password as separate arguments. DSN syntax is driver-specific, and not all options are supported across all databases. Proper error handling and security practices, such as avoiding hard-coded credentials, are important when constructing and using DSNs.

See also: PHP Data Objects, DSN, PDO drivers, database connection practices.