A function and subfunctions to find links to the same content on two different sites (of different languages) - for use on myoncofertility.org

get_alternate_language_link.php

<?php

/**
 * get_alternate_language_link
 * returns a full url to a page on the other language site
 * or returns false if the page doesn't exist in the other language
 *
 * Arguments: $path (optional)
 *    if a path is supplied (e.g. 'node/4')
 *    the alternate link to that path will be returned
 *    $path defaults to the current page
 *
 * Example:
 * $alternate_link = get_alternate_language_link();
 * if($alternate_link)
 *   echo "<a href='$alternate_link'>See this page in spanish</a>";
 *
 */

function get_alternate_language_link( $path=NULL ) {
  if(empty($path))
    $path = get_current_page_path();
  $debug = false; // print url whether page exists or not
  global $base_url;
  $current_language = get_current_language();

  switch( $current_language ) {
    case 'es':
      $base = substr($base_url, 0, -3);
      break;

    case 'en':
      $base = $base_url . '/es';
      break;
  }

  $url = $base . '/' . $path;

  if($debug)
    echo "Alternate link: $url\n";

  if( page_exists( $url ) )
    return $url;
  else
    return false;
}

function get_current_language() {
  global $base_url;
  $pattern = '/\/es$/';
  if( preg_match( $pattern, $base_url ) )
    return 'es';
  else
    return 'en';
}

function page_exists( $url ) {
  // This function will use libcurl if it is installed,
  // or execute curl at command line if not.

  // This function is currently untested as bion does not have
  // libcurl installed. I think it should work as-is though.
  if( extension_loaded( 'libcurl' ) ) {
    $curl = curl_init();
      curl_setopt($curl, CURLOPT_URL, $url);
      curl_setopt($curl, CURLOPT_HEADER, true);
      curl_setopt($curl, CURLOPT_NOBODY, true);
    $header = curl_exec($curl);
    $response = curl_getinfo( $curl );
  }
  else {
    exec('curl -I "'.$url.'"', $output);
    // I'd much rather use libcurl than exec curl,
    // but from what I can tell, libcurl isn't installed
    // in bion's php build.
    // if the production server has libcurl, I can rewrite this in pure php
    $pattern = '/\d{3}/';
    preg_match( $pattern, $output[0], $matches );
    $response = $matches[0];
  }
  return ($response == 200);
}

function get_current_page_path() {
  return implode('/', arg() );
}

function print_link_if_exists() {
  $link = get_alternate_language_link( get_current_page_path() );
  if( $link )
    echo "Page exists at $link";
  else
    echo "Page does not exist";
}

?>