PHP client for Systeme.io API

systeme-api.php

<?php

class Systeme_API {
	const API_URL = 'https://api.systeme.io/api';

	public function __construct( private string $api_key ) {}

	private function url_to( string $endpoint, ?array $params = [] ): string {
		$url = sprintf( '%s/%s', self::API_URL, ltrim( $endpoint, '/' ) );

		if ( ! empty( $params ) ) {
			return $url . '?' . http_build_query( $params );
		}

		return $url;
	}

	private function get_context( string $method, ?array $body = [] ) {
		$headers = [
			'X-API-Key'  => $this->api_key,
			'Accept' => 'application/json',
			'Content-Type' => 'application/json',
		];

		return stream_context_create( 
			[
				'http' => [
					'ignore_errors' => true,
					'method' => strtoupper( $method ),
					'header' => implode( "\r\n", array_map( fn( $k, $v ) => "$k: $v", array_keys( $headers ), $headers ) ),
					'content' => ! empty( $body ) ? json_encode( $body ) : null,
				],
			] 
		);
	}

	private function call( string $method, string $endpoint, ?array $params = [], ?array $body = [] ): array {
		$response = file_get_contents( 
			$this->url_to( $endpoint, $params ), 
			false, 
			$this->get_context( $method, $body )
		);

		if ( function_exists( 'http_get_last_response_headers' ) ) {
			$response_headers = http_get_last_response_headers();
		} else {
			// $response_headers = @$http_response_header;
		}

		preg_match( '/HTTP\/\d\.\d\s+(\d{3})/', $response_headers[0], $matches );

		if ( false === $response ) {
			$error = error_get_last();
			throw new RuntimeException( $error['message'] ?? 'Unknown error occurred while making API request.' );
		}

		return [
			'status' => (int) $matches[1],
			'body' => json_decode( $response, true ),
		];
	}

	private function get( string $endpoint, ?array $params = [] ): array {
		return $this->call( 'GET', $endpoint, $params )['body'];
	}

	private function post( string $endpoint, ?array $body = [] ) {
		$this->call( 'POST', $endpoint, null, $body );
	}

	public function get_contacts(): array {
		$contacts = $this->get( 'contacts', [ 'limit' => 100 ] );

		return $contacts['items'];
	}

	public function get_students( string $course_id ): array {
		$students = $this->get( 'school/enrollments', [
			'course' => $course_id,
			'limit' => 100,
		] );

		return $students['items'];
	}

	public function get_tags(): array {
		$tags = $this->get( 'tags', [ 'limit' => 100 ] );

		return $tags['items'];
	}

	public function set_tag( string $contact_id, int $tag_id ) {
		$this->post( 
			sprintf( 'contacts/%s/tags', $contact_id ), 
			[ 'tagId' => $tag_id ]
		);
	}
}