Custom module (php) - invoking connection

Hello,

I need to write a custom module/server extension in PHP to export a portion of my MySQL database.
I’m struggling to find the portion of code to invoke the current connection from wappler
(what otherwise would be something along the lines of $DBH = new PDO("mysql:host=".$DBHOST.";dbname=".$DBNAME."; charset=utf8", $DBUSER, $DBPASS);), so I can then run construct my queries and write a SQL file with their output.

Thanks for the help!