source: sipes/modules_contrib/highcharts/highcharts.install @ 6e81fb4

<?php

/**
 * Implementation of hook_requirements().
 * Based on code from "3 Tips For Using External Libraries With Drupal":
 * http://engineeredweb.com/blog/10/5/3-tips-using-external-libraries-drupal
 */
function highcharts_requirements($phase) {
  $requirements = array();
  // Ensure translations do not break at install time
  $t = get_t();

  $requirements['highcharts'] = array(
    'title' => $t('Highcharts Library'),
  );

  if ($phase == 'install') {
    if (!module_exists('libraries')) {
      $requirements['highcharts']['severity'] = REQUIREMENT_ERROR;
      $requirements['highcharts']['description'] = $t('Please download and enable libraries module before enabling this module.');
    }

    return $requirements;
  }

  $libraries = libraries_get_libraries();
  if (isset($libraries['highcharts'])) {
    $requirements['highcharts']['value'] = $t('Installed');
    $requirements['highcharts']['severity'] = REQUIREMENT_OK;
  }
  else {
    if ($phase=='runtime') {
      $requirements['highcharts']['value'] = $t('Not Installed');
    }
    $requirements['highcharts']['severity'] = REQUIREMENT_ERROR;
    $requirements['highcharts']['description'] = $t('The Highcharts module was not installed. Please download the Highcharts library (%url) before installing the Highcharts module. See the README.txt file for more information.', array('%url' => 'http://www.highcharts.com/download'));
  }

  return $requirements;
}