PHP SQLSRV Extension, or ODBC. If attaching remotely, you need to configure SQL Express to allow remote connections and open ports in your Firewall.
Depends if you are using SQL Express or SQL Local DB, but you are looking for MDF/LDF files. SQL Server Management Studio (SSMS) will allow you to see the properties of the database and reveal where the files are located. But that does not really help in your quest, since you need the DBMS Engine to read the files anyway.
Search for Data Exports feature - it uses Report Tags to export to different data formats including CSV, XML, YAML, etc… This is the most detailed discussion I could find…