Creating a Self-Updating WordPress Post Using WordPress Transients and Data from a Third Party API

In the post Pondering a Jupyter Notebooks to WordPress Publishing Pattern: MultiMarker Map Widget, I described a simple pattern I started exploring last year that used a custom WordPress shortcode plugin to render data added to one or more custom fields associated with a WordPress post; the post text (including shortcode) and custom fields data were themselves posted into WordPress using some Python code executed from a Jupyter notebook. The idea behind that pattern was to provide a way of automating the creation of custom posts largely from a supplied data set, rendered using a generic shortcode plugin.

Another pattern I explored last year used the WordPress Transients API to cache data pulled from a 3rd party API in the WordPress database, and allow that data to be used by a custom plugin to render the post.

Here’s some example code for a plugin that renders a map containing recent planning applications on the Isle of Wight: the data is grabbed via an API from a webscraper, which scrapes the data from the Isle of Wight council website.

The two key bits of the script are where I check to see if cached data exisits ( get_transient( 'iwcurrplanningitems' ); and if it doesn’t, grab a recent copy from the API and cache it for 8 hours (set_transient('iwcurrplanningitems', $markers, 60*60*8);).

Plugin Name: IWPlanningLeafletMap
Description: Shortcode to render an interactive map displaying clustered markers. Markers are pulled in via JSON from an external URL. Intended primarily to supported automated post creation. Inspired by folium python library and Google Maps v3 Shortcode multiple Markers WordPress plugin
Version: 1.0
Author: Tony Hirst

//Loaded in from multimarker shortcode
add_action( 'wp_enqueue_scripts', 'custom_scripts' );
add_action( 'wp_enqueue_scripts', 'custom_styles' );

// Add stuff to header
add_action('wp_head', 'IWPlanningLeafletMap_header');
add_action('wp_head', 'fix_css');

function fix_css() { 
	echo '<style type="text/css">#map {
      }</style>' . "\n";

function IWPlanningLeafletMap_header() {

function IWPlanningLeafletMap_call($attr) {
// Generate the map template

	// Default attributes - can be overwritten from shortcode
	$attr = shortcode_atts(array(	
									'lat'   => '50.675', 
									'lon'    => '-1.32',
									'id' => 'iwmap_1',
									'zoom' => '11',
									'width' => '800',
									'height' => '500',
									), $attr);

	$html = '<div class="folium-map" id="'.$attr['id'].'" style="width: '. $attr['width'] .'px; height: '. $attr['height'] .'px"></div>

   <script type="text/javascript">
      var base_tile = L.tileLayer("https://{s}{z}/{x}/{y}.png", {
          maxZoom: 18,
          minZoom: 1,
          attribution: "Map data (c) OpenStreetMap contributors -"

      var baseLayer = {
        "Base Layer": base_tile

      list of layers to be added
      var layer_list = {

      Bounding box.
      var southWest = L.latLng(-90, -180),
          northEast = L.latLng(90, 180),
          bounds = L.latLngBounds(southWest, northEast);

      Creates the map and adds the selected layers
      var map ="'.$attr['id'].'", {
                                       center:['.$attr['lat'].', '.$attr['lon'].'],
                                       zoom: '.$attr['zoom'].',
                                       maxBounds: bounds,
                                       layers: [base_tile]

      L.control.layers(baseLayer, layer_list).addTo(map);

      //cluster group
      var clusteredmarkers = L.markerClusterGroup();
      //section for adding clustered markers
	$markers =  get_transient( 'iwcurrplanningitems' );
	if ( false === $markers ) {
		$json = file_get_contents($url);
		$markers=json_decode($json, true);
		set_transient('iwcurrplanningitems', $markers, 60*60*8);
	for ($i = 0;$i < count($markers);$i ++){
		$arrkeys=['Agent or Applicant','Location','Proposal'];
		foreach($arrkeys as $arrkey){
			$markers[$i][$arrkey] = str_replace("\n", "<br/>", $markers[$i][$arrkey]);
			$markers[$i][$arrkey] = str_replace("\r", "<br/>", $markers[$i][$arrkey]);
		$html .='
			var marker_'.$i.'_icon = L.AwesomeMarkers.icon({ icon: "info-sign",markerColor: "blue",prefix: "glyphicon",extraClasses: "fa-rotate-0"});
      		var marker_'.$i.' = L.marker(['.$markers[$i]['lat'].','.$markers[$i]['lon'].'], {"icon":marker_'.$i.'_icon});
      marker_'.$i.'.bindPopup("<strong>Consultation start:</strong> '.$markers[$i]['Consultation Start Date'].'<br/><strong>Consultation end:</strong> '.$markers[$i]['Consultation End Date'].'<br/><strong>Location:</strong> '.$markers[$i]['Location'].'<br/><em> '.$markers[$i]['Parish'].' parish, '.$markers[$i]['Ward'].' ward.</em><br/><strong>Proposal:</strong> '.$markers[$i]['Proposal'].'<br/><strong>Agent or Applicant:</strong> '.$markers[$i]['Agent or Applicant'].'<br/><strong>Case Officer:</strong> '.$markers[$i]['Case Officer'].'<br/><em><a href=\''.$markers[$i]['stub'].'\'>View application</a></em>");
      marker_'.$i.'._popup.options.maxWidth = 300;
     		//add the clustered markers to the group anyway

	$html .= '</script>';
	return $html;

add_shortcode('IWPlanningLeafletMap', 'IWPlanningLeafletMap_call');

One thing I started to wonder over the Christmas break was whether this approach could provide a way of sharing “data2text” content. For example, having a plugin that creates a canned summary of jobseeker’s allowance figures from data cached from the ONS website? A downside of this is that I’d have to write the data2text script using PHP, which means I couldn’t directly build on related code I’ve written previously…

I also wonder if we could use custom fields to permanently store data for a particular post. For example, we might check whether or not a custom field exists for the post, and if it doesn’t we could create and populate it using data pulled from an API, (possibly keyed by plugin/shortcode parameters, or the post publication date), using a WordPress add_post_meta() function call?

Author: Tony Hirst

I'm a Senior Lecturer at The Open University, with an interest in #opendata policy and practice, as well as general web tinkering...

2 thoughts on “Creating a Self-Updating WordPress Post Using WordPress Transients and Data from a Third Party API”

  1. So the only content in the post is the rendered map? I might be missing an element. Are you creating new posts to show how the maps change over time? Ot just a single post with a map the changes as the data does

    This seems to me the purpose of custom fields, plus keeping the data. You could still use transient fields as an indicator whether to create a new post?

    1. @cogdog The plugin is actually a shortcode that just inserts a map into a post, yes. On the demo page, the full content of my post was:




      The rationale behind the use of transients was:

      • scraper that feeds the API updates once a day, but could be any time of day;
      • there is a single post that shows data from the API for applications in last 28 days;
      • I don’t know when the API updates, I can’t hammer the API, I don’t know when a person will view the post, or how many;
      • if the post is viewed only rarely, the transient data will have disappeared so call the API;
      • if the page is being hit repeatedly, then use the transient data (I know I can’t rely on it, but I also want it to expire every so often);

      The current set up means the data should only be at most 8 hours out of date, and the API won’t be hit if the post is never viewed or is viewed repeatedly in a short time.

      I so far don’t have a WordPress script that will automatically create a new, current/updated post each day,

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