How Do I Connect PHP Email Script to Postfix?

I have a VPS where I’ve installed my site files, including the PHP email script that uses the php mail() function inside of the following directory (how my site directory/path is set up):

/var/www/mywebsite.com/html/ https://ibb.co/XF1JFvv

And when I installed Postfix, I’ve configured it to send email through Amazon SES. Postfix has been installed inside of the following directory:

/etc/postfix/ https://ibb.co/2SDjb8z

The problem that I’m having is that it will send email from the command line when testing that Postfix has properly installed along with using the Amazon SES SMTP, BUT my php email script DOESN’T connect from my websites folder directory to Postfix.

How do I connect my php email script to Postfix? Do I need to change directories?

Here is the php mail() function script that I’m using below:

<?php
$to = "MyTestEmailAddress@gmail.com";
$subject = "Another Test!";
$txt = "Hello world!";
$headers = "From: MyEmailAddress@gmail.com" . "\r\n" .
"CC: AnotherTestEmailAddress.com";

mail($to,$subject,$txt,$headers);
?>