(WP) Create your ownRest API endpoints

example-rest-api.php

<?php

add_action('rest_api_init', function () {
	register_rest_route('custom/v1', '/transactions/', [
	  'methods' => 'GET',
	  'callback' => 'get_transactions',
	]);
  });

  function get_transactions($request) {

	$paged = $request->get_param('page') ? $request->get_param('page') : 1;
	$year  = $request->get_param('year') ? $request->get_param('year') : NULL;

	$args = [
		'post_type' => 'transaction',
		'posts_per_page' => -1,
		'paged' => $paged,
		'tax_query' => [],
		'orderby'=> 'date',
		'order'		=> 'DESC'
	];

	if($year) {
		$args['meta_query'] = [
			[
				'key'     => 'transaction_announcement_date',
				'compare' => 'LIKE',
				'value'   => $year,
			],
		];
	}

	$taxonomies = [
	  'transaction-type' => 'transaction-type',
	  'location' => 'location',
	  'sector' => 'sector',
	  'subsector' => 'subsector',
	];

	foreach ($taxonomies as $param => $taxonomy) {
	  if (!empty($request->get_param($param))) {
		$args['tax_query'][] = [
		  'taxonomy' => $taxonomy,
		  'field' => 'slug',
		  'terms' => explode(',', $request->get_param($param)),
		];
	  }
	}

	$query = new WP_Query($args);

	if ($query->have_posts()) {
	  $transactions = [];
	  while ($query->have_posts()) {
		$query->the_post();
		$transactions[] = [
		  'ID' 		=> get_the_ID(),
		  'title' 	=> get_the_title(),
		  'link'	=> get_permalink(),
		  'year'	=> wp_date('Y', strtotime(get_field('transaction_announcement_date'))),
		  'content' => get_the_content(),
		  'acf'     => get_fields(),
		];
	  }
	  wp_reset_postdata();


	  return new WP_REST_Response($transactions, 200);
	} else {
	  return new WP_Error('no_transactions', 'No transactions found', ['status' => 404]);
	}
  }