engelsystem/includes/pages/user_atom.php

<?php

/**
 * Publically available page to feed the news to feedreaders
 */
function user_atom()
{
    global $user, $display_news;

    if (!isset($_REQUEST['key']) || !preg_match("/^[0-9a-f]{32}$/", $_REQUEST['key'])) {
        engelsystem_error("Missing key.");
    }
    $key = $_REQUEST['key'];

    $user = User_by_api_key($key);
    if ($user == null) {
        engelsystem_error("Key invalid.");
    }
    if (!in_array('atom', privileges_for_user($user['UID']))) {
        engelsystem_error("No privilege for atom.");
    }

    $news = sql_select("
        SELECT *
        FROM `News` 
        " . (empty($_REQUEST['meetings']) ? '' : 'WHERE `Treffen` = 1 ') . "
        ORDER BY `ID`
        DESC LIMIT " . (int)$display_news
    );

    $output = make_atom_entries_from_news($news);

    header('Content-Type: application/atom+xml; charset=utf-8');
    header("Content-Length: " . strlen($output));
    raw_output($output);
}

/**
 * @param array[] $news_entries
 * @return string
 */
function make_atom_entries_from_news($news_entries)
{
    $html = '<?xml version="1.0" encoding="utf-8"?>
  <feed xmlns="http://www.w3.org/2005/Atom">
  <title>Engelsystem</title>
  <id>' . $_SERVER['HTTP_HOST']
        . htmlspecialchars(preg_replace(
            '#[&?]key=[a-f0-9]{32}#',
            '',
            $_SERVER['REQUEST_URI']
        ))
        . '</id>
  <updated>' . date('Y-m-d\TH:i:sP', $news_entries[0]['Datum']) . "</updated>\n";
    foreach ($news_entries as $news_entry) {
        $html .= make_atom_entry_from_news($news_entry);
    }
    $html .= "</feed>";
    return $html;
}

function make_atom_entry_from_news($news_entry)
{
    return "  <entry>
    <title>" . htmlspecialchars($news_entry['Betreff']) . "</title>
    <link href=\"" . page_link_to_absolute("news_comments&amp;nid=") . "${news_entry['ID']}\"/>
      <id>" . preg_replace('#^https?://#', '', page_link_to_absolute("news")) . "-${news_entry['ID']}</id>
      <updated>" . date('Y-m-d\TH:i:sP', $news_entry['Datum']) . "</updated>
    <summary type=\"html\">" . htmlspecialchars($news_entry['Text']) . "</summary>
    </entry>\n";
}