How to generate AWS SES SMTP passwords from an already existing IAM User secret key. In PHP. See https://docs.aws.amazon.com/ses/latest/DeveloperGuide/smtp-credentials.html#smtp-credentials-convert

generate_aws_ses_password.php

<?php

$key = getenv('AWS_SECRET_ACCESS_KEY');
if (!$key) {
    throw new \LogicException('Missing AWS_SECRET_ACCESS_KEY');
}

$sig = hash_hmac('sha256', 'SendRawEmail', $key, true);

echo base64_encode(pack('C', 0x02) . $sig), PHP_EOL;