WordPress AJAX example for Liturgical Calendar API

plugin.js

	jQuery(document).ready(function($) {

		var data = {
			'action': 'call_litcal_api',
			'nationalpreset': 'USA'
		};

		// since 2.8 ajaxurl is always defined in the admin header and points to admin-ajax.php
		jQuery.get(ajaxurl, data, function(response) {
			alert('Got this from the LitCal API: ' + response);
		});
	});

plugin.php

define("TRANSIENT_PREFIX","LitCal_");		

function callLitCalAPI(){

    //build the querystring from the GET or POST parameters, we're using GET here...
    $querystring = "";
    //see the allowed parameters here: https://johnromanodorazio.com/LiturgicalCalendar/dist/#/Main%20API%20endpoint/retrieveEventsGET
    $allowedParameters = ["diocesanpreset","nationalpreset","locale","epiphany","ascension","corpuschristi","year","returntype"];
    $parameters = [];
    foreach($allowedParameters as $param){
      if(isset($_GET[$param])){
        $parameters[] = $param . "=" . $_GET[$param];
      }
    }
    $querystring = implode("&",$parameters);

    //if we don't already have the information stored in a transient,
    //then we will call the API endpoint
    if (false === ($output = get_transient(TRANSIENT_PREFIX.md5($querystring)))) {
        //We will make a secure connection to the BibleGet service endpoint,
        //if this server's OpenSSL and CURL versions support TLSv1.2
        $curl_version = curl_version();
        $ssl_version = str_replace('OpenSSL/', '', $curl_version['ssl_version']);
        if (version_compare($curl_version['version'], '7.34.0', '>=') && version_compare($ssl_version, '1.0.1', '>=')) {
            //we should be good to go for secure SSL communication supporting TLSv1_2
            $ch = curl_init("https://johnromanodorazio.com/LiturgicalCalendar/LitCalEngine.php?" . $querystring);
            curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, TRUE);
            curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, 2);
            curl_setopt($ch, CURLOPT_SSLVERSION, CURL_SSLVERSION_TLSv1_2);
        } else {
            $ch = curl_init("http://johnromanodorazio.com/LiturgicalCalendar/LitCalEngine.php?" . $querystring);
        }

        curl_setopt($ch, CURLOPT_RETURNTRANSFER, TRUE);

        if (ini_get('safe_mode') || ini_get('open_basedir')) {
            // if safe mode is on, we can't use some settings
        } else {
            curl_setopt($ch, CURLOPT_FOLLOWLOCATION, TRUE);
            curl_setopt($ch, CURLOPT_AUTOREFERER, TRUE);
        }
        $output = curl_exec($ch);
        if ($output && !curl_errno($ch)) {
          //we seem to have successfully retrieved our JSON data from the API
        } else {
            $errs = new stdClass();
            $errs->error = "There was an error communicating with the Liturgical Calendar API, please wait a few minutes and try again" . ': '' . curl_error($ch) . '': ' . $finalquery;
            $output = json_encode($errs);
        }
        curl_close($ch);

        //this will ensure that the API endpoint will not be called more than once every 7 days
        set_transient(TRANSIENT_PREFIX.md5($querystring), $output, 7 * 24 * HOUR_IN_SECONDS);
    }

    echo $output;
    wp_die();
}

add_action('wp_ajax_call_litcal_api', 'callLitCalAPI');