Best practice securing SQL Database Credentials with PHP

I currently have a web pages which pull data from an SQL database and display it using php to handle the connection and query.

I am currently using this snippet in my PHP file to connect and pull data:

$conn = odbc_connect(
    "DRIVER={SQL Server Native Client 10.0};Server=xxx.xxx.xxx.xxx;Database=databasename", "username", "password");
if (!($conn)) { 
    echo "<p>Connection to DB via ODBC failed: ";
    echo odbc_errormsg ($conn );
    echo "</p>\n";
}

Does anyone see vulnerability with this and is there practice I should use?