edd_complete_purchase.php

<?php

/***
Do something with payment data after purchase
***/

function drw_api_call_after_purchase( $payment_id ) {
	
	$payment_meta = edd_get_payment_meta( $payment_id );
	
	$cart_items = edd_get_payment_meta_cart_details( $payment_id );
	
	$user_id = $payment_meta['user_info']['id'];

	foreach ( $cart_items as $download ) {
            
		//make API call
		drw_update_email_api( $user_id, $download['id'] );

	}
}

add_action( 'edd_complete_purchase', 'drw_enroll_after_purchase' );