使用php显示搜索引擎来的关键词

以下是相关实现代码：

代码如下:
<?php
/*
Plugin Name: display-search-keywords
Plugin URI: http://www.imyxiao.com/1531.html
Description: 当访客通过搜索引擎来到你的博客，这个插件可以显示访客搜索的关键词
Version: 1.0
Author:<a href="http://www.imyxiao.com/">仰肖</a>
*/
function unescape($str) {
 $ret = '';
 $len = strlen($str);
 for ($i = 0; $i < $len; $i++) {
  if ($str[$i] == '%' && $str[$i +1] == 'u') {
   $val = hexdec(substr($str, $i +2, 4));
   if ($val < 0x7f)
    $ret .= chr($val);
   else
    if ($val < 0x800)
     $ret .= chr(0xc0 | ($val >> 6)) . chr(0x80 | ($val & 0x3f));
    else
     $ret .= chr(0xe0 | ($val >> 12)) . chr(0x80 | (($val >> 6) & 0x3f)) . chr(0x80 | ($val & 0x3f));

   $i += 5;
  } else
   if ($str[$i] == '%') {
    $ret .= urldecode(substr($str, $i, 3));
    $i += 2;
   } else
    $ret .= $str[$i];
 }
 return $ret;
}
function ls_get_delim($ref) {
 $search_engines = array (
  'google.com.hk' => 'q',
  'google.com.tw' => 'q',
  'go.google.com' => 'q',
  'google.com' => 'q',
  'blogsearch.google.com' => 'q',
  'cn.bing.com' => 'q',
  'one.cn.yahoo.com' => 'p',
  'baidu.com' => 'wd',
  'soso.com' => 'w',
  'youdao.com' => 'q',
  'sogou.com' => 'query'
 );
 $delim = false;
 // 判断
 if (isset ($search_engines[$ref])) {
  $delim = $search_engines[$ref];
 }
 return $delim;
}

function ls_get_refer() {
 // 判断前一页面的 URL 地址
 $queryString = $_GET['referer'];
 $queryString = unescape($queryString);
 if (!isset ($queryString) || ($queryString == ''))
  return false;
 $referer_info = parse_url($queryString);
 $referer = $referer_info['host'];
 //去除www.
 if (substr($referer, 0, 4) == 'www.')
  $referer = substr($referer, 4);
 return $referer;
}

function ls_getinfo($what) {
 $referer = ls_get_refer();
 if (!$referer)
  return false;
 $delimiter = ls_get_delim($referer);
 if ($delimiter) {
  $terms = ls_get_terms($delimiter);
  if ($what == 'isref' && $terms != '') {
   return true;
  }
  if ($what == 'terms') {
   echo $terms;
  }
 }
 return false;
}

function yxiao_seems_utf8($str) {