各位麻烦指点下get_content的有关问题

<?php

  $ROBOT['baidu']['name'] = '百度';
  $ROBOT['baidu']['site_url'] = 'http://www.baidu.com/s?wd=site%3A';
  $ROBOT['baidu']['site_pattern'] = "/找到相关网页约(.*)篇/";
  $ROBOT['baidu']['link_url'] = 'http://www.baidu.com/s?wd=domain%3A';
  $ROBOT['baidu']['link_pattern'] = "/找到相关网页约(.*)篇/";
  
  $bot='baidu';
  $domain='www.27dao.com';
  
  $content = '';
  $site_info = '';
  $link_info = '';
  if(empty($content)) echo 'Unkown Error...';
  $content = get_content($ROBOT[$bot]['site_url'].$domain);
  if(preg_match($ROBOT[$bot]['site_pattern'], $content, $matches)) $site_info = $matches[1];
  $content = get_content($ROBOT[$bot]['link_url'].$domain);
  if(preg_match($ROBOT[$bot]['link_pattern'], $content, $matches)) $link_info = $matches[1];
  
  echo $ROBOT[$bot]['name']."收录:".$domain."<a href=".$ROBOT[$bot]['site_url'].$domain.">".$site_info."</a>";
  
?>
提示Fatal error: Call to undefined function get_content()。
怎么回事啊？

file_get_contents()。