How to access Postgres .pgpass file from php?

I have my php files in the web root, and the Postgres 10 logon credentials are in the php file.  I want to put them outside the web root for security, because a malicious robot could easily read the credentials. 

After research, I found the .pgpass file.  That looks like the ideal solution, but after even more research, I haven't found how to use that file from a php logon script. 

Here is the section from my php script:

$dsn = vsprintf('pgsql:host=%s;port=%s;dbname=%s;user=%s;password=%s', [

    'host' => '000.00.00.00',

    'port' => '5432',

    'dbname' => '[dbname]',

    'user' => '[username]',

    'password' => '[password]',

]);

Currently I store the real dbname, user and password in the php.  My questions are:

1. How can I access it from the .pgpass file instead? 

2. Where is .phpass loccated in Apache2 Ubuntu 18.04?

Thanks for any help with this.