Hook into Sensei start and end course.

sensei_hooks.php

<?php
/**
 * Hook in and do an action when a user starts a course.
 * This works for WooCommerce purchased courses and free courses.
 */
add_filter( 'sensei_user_course_start', 'convertkit_sensei_user_course_start', 10, 2 );
function convertkit_sensei_user_course_start( $user_id, $course_id ) {

	if ( $user_id ) {
		$user = get_userdata( $user_id );
		$email = $user->user_email;

		// Zap URL
		$url = '';
		$payload = array(
			'email' => $email,
			'user_id' => $user_id,
			'action' => 'started',
			'course_id' => $course_id,
		);

		// Setup request args.
		$http_args = array(
			'method'      => 'POST',
			'timeout'     => MINUTE_IN_SECONDS,
			'redirection' => 0,
			'httpversion' => '1.0',
			'blocking'    => true,
			'user-agent'  => 'ConvertKit Webhook',
			'body'        => trim( json_encode( $payload ) ),
			'headers'     => array( 'Content-Type' => 'application/json' ),
			'cookies'     => array(),
		);

		// Webhook away!
		$response = wp_safe_remote_request( $url, $http_args );
	}

}

/**
 * Hook in and do an action when a user finishes a course.
 */
add_action( 'sensei_user_course_end', 'convertkit_sensei_user_course_end', 10, 2 );
function convertkit_sensei_user_course_end( $user_id, $course_id ) {

	if ( $user_id ) {
		$user = get_userdata( $user_id );
		$email = $user->user_email;

		// Zap URL
		$url = '';
		$payload = array(
			'email' => $email,
			'user_id' => $user_id,
			'action' => 'completed',
			'course_id' => $course_id,
			);

		// Setup request args.
		$http_args = array(
			'method'      => 'POST',
			'timeout'     => MINUTE_IN_SECONDS,
			'redirection' => 0,
			'httpversion' => '1.0',
			'blocking'    => true,
			'user-agent'  => 'ConvertKit Webhook',
			'body'        => trim( json_encode( $payload ) ),
			'headers'     => array( 'Content-Type' => 'application/json' ),
			'cookies'     => array(),
		);

		// Webhook away!
		$response = wp_safe_remote_request( $url, $http_args );
	}
}