For Custom Audience API integration, check out Meta documentation.

The general Meta API info is a good place to start.

Then the next steps are:

1. Install the Meta Ads API PHP SDK.

2. Specify the audience.
   • Use an existing custom audience. See below for PHP code sample for adding people to it.
     --OR--
   • Create a new custom audience. See below for PHP code sample.

Add people to an existing custom audience (<CUSTOM_AUDIENCE_ID>) (PHP code example):

<?php

use FacebookAds\Object\CustomAudience;
use FacebookAds\Object\Values\CustomAudienceTypes;

$emails = array(
  'test1@example.com',
  'test2@example.com',
  'test3@example.com',
);

$audience = new CustomAudience(<CUSTOM_AUDIENCE_ID>);

$audience->addUsers($emails, CustomAudienceTypes::EMAIL);

?>

Create a custom audience: PHP code sample

<?php

use FacebookAds\Object\CustomAudience;
use FacebookAds\Object\Fields\CustomAudienceFields;
use FacebookAds\Object\Values\CustomAudienceSubtypes;

$audience = new CustomAudience(null, 'act_<AD_ACCOUNT_ID>');
$audience->setData(array(
  CustomAudienceFields::NAME => 'My new CA',
  CustomAudienceFields::SUBTYPE => CustomAudienceSubtypes::CUSTOM,
  CustomAudienceFields::DESCRIPTION => 'People who bought from my website',
));

$audience->create();

?>

More code examples at https://developers.facebook.com/docs/marketing-api/audiences-api

Our Technical Account Managers are happy to help with the implementation.