$serverName = "serverName";
$connectionInfo = array( "Database"=>"DbName",
"UID"=>"UserName",
"PWD"=>"Password",
"Encrypt"=>true,
"TrustServerCertificate"=>true);
$conn = sqlsrv_connect( $serverName, $connectionInfo);
Źródło: https://stackoverflow.com/questions/14959492/connecting-to-mssql-from-php-securely-with-encryption