Currency switcher class for use with WordPress.

README.md

Currency switcher class

Use this class to show prices in different currencies. Use add_filter to change the output of the function that shows prices to a different currency like this (the example is for Lava RealEstate):

function gonzo_price( $price, $post_id ){
  global $post, $gonzo_cw;

  if( !$post_id )
    $post_id  = $post->ID;

  return $gonzo_cw->format( $gonzo_cw->convert( intVal( get_post_meta( $post_id, '_price', true ) ), 0 ) );

}
add_filter( 'lava_realestate_price', 'gonzo_price', 10, 2 );

The current implementation has a base currency in GBP.

License

Licensed under (WTFPL)[http://www.wtfpl.net/]

class_CurrencySwitcher.php

<?php
class CurrencySwitcher {

  private $currencies = array (
    'gbp' => array ( 'sign' => '£', 'position' => 'before', 'rate' => 1, 'name' => 'British Pound', 'short' => 'GBP' ),
    'eur' => array ( 'sign' => '€', 'position' => 'before', 'rate' => 1.142530706, 'name' => 'Euro', 'short' => 'EUR' ),
    'usd' => array ( 'sign' => '$', 'position' => 'before', 'rate' => 1.02771855, 'name' => 'US Dollar', 'short' => 'USD' ),
    'aud' => array ( 'sign' => '$', 'position' => 'before', 'rate' => 1.730482852, 'name' => 'Australian Dollar', 'short' => 'AUD' )
  );

  private $currency = 'gbp';

  public function __construct( $default ){
    if( array_key_exists( $default, $this->currencies ) ){
      $this->currency = $default;
    }
    add_action( 'init', array( $this, 'set_currency' ) );
    add_action( 'gonzo_daily', array( $this, 'get_rates' ) );
    $this->set_rates();
  }

  public function get_rates(){

    $ratesURL = 'https://www.ecb.europa.eu/stats/eurofxref/eurofxref-daily.xml';

    $response = wp_remote_get( $ratesURL, array( 'user-agent' => 'Mozilla/5.0 (X11; Linux x86_64; rv:57.0) Gecko/20100101 Firefox/57.0' ) );

    $ratesXML = new SimpleXMLElement( $response['body'] );

    $currencies = array_keys( $this->currencies );
    // We put a default EUR rate that we will later reference to GBP
    $rates = array( 'eur' => 1 );

    foreach( $ratesXML->Cube->Cube->Cube as $rate ){
      $currency = strtolower( $rate['currency'] );
      if( in_array( $currency, $currencies ) ) {
        $rates[$currency] = (float)$rate['rate'];
      }
    }

    if( $rates['gbp'] != 0 ) {

      $eur2gbp = 1 / $rates['gbp'];

      foreach( $currencies as $currency ){
        $rates[$currency] =  round( $eur2gbp * $rates[$currency], 4 );
      }

      set_transient( 'gonzo_currency_rates', $rates, 48 * HOUR_IN_SECONDS );

      return $rates;

    }

    return false;

  }

  private function set_rates(){

    if ( false === ( $rates = get_transient( 'gonzo_currency_rates' ) ) ) {
      if ( true === ( $rates = @$this->get_rates() ) ) {
        set_transient( 'gonzo_currency_rates', $rates, 48 * HOUR_IN_SECONDS );
      }
    }

    if( $rates ) {
      foreach ( $this->currencies as $key => $currency ) {
        if( $rates[$key] != 0 ) {
          $this->currencies[$key]['rate'] = $rates[$key];
        }
      }
    }

  }

  public function set_currency(){
    if( isset( $_GET['currency'] ) ){
      if( array_key_exists( $_GET['currency'], $this->currencies ) ){
        $this->currency = $_GET['currency'];
      }
      $expiry = strtotime('+1 year');
      setcookie( 'currency', $this->currency, $expiry, COOKIEPATH, COOKIE_DOMAIN );
    }
    elseif ( isset( $_COOKIE['currency'] ) ) {
      if( array_key_exists( $_COOKIE['currency'], $this->currencies ) ){
        $this->currency = $_COOKIE['currency'];
      }
    }
  }

  public function get_currency(){
    return $this->currency;
  }

  public function get_currencies(){
    return $this->currencies;
  }

  public function format( $price ) {
    $currency = $this->currencies[$this->currency];
    if( $currency['position'] == 'before' ){
      return $currency['sign'] . '' . number_format_i18n( $price );
    }
    else {
      return number_format_i18n( $price ) . '' . $currency['sign'];
    }
  }

  public function convert( $price, $precision ){
    return round( $price * $this->currencies[$this->currency]['rate'], $precision );
  }

}

$gonzo_cw = new CurrencySwitcher( 'gbp' );

?>

plugin.php

<?php
/**
 * In plugin activation and deactivation hooks register sheduled job to execute rates update.
 */
function gonzo_activate(){
  if ( ! wp_next_scheduled ( 'gonzo_daily' ) ) {
    wp_schedule_event( time(), 'daily', 'gonzo_daily' );
  }
}
register_activation_hook( __FILE__, 'gonzo_activate' );

function tnac_deactivate() {
  wp_clear_scheduled_hook('gonzo_daily');
}
register_deactivation_hook(__FILE__, 'gonzo_deactivate');
?>