<?php
function search_word_from() {
 $referer = isset($_SERVER['HTTP_REFERER'])?$_SERVER['HTTP_REFERER']:'';
 if(strstr( $referer, 'baidu.com')){ //百度
  preg_match( "|baidu.+wo?r?d=([^\\&]*)|is", $referer, $tmp );
  $keyword = urldecode( $tmp[1] );
  $from = 'baidu';
 }elseif(strstr( $referer, 'google.com') or strstr( $referer, 'google.cn')){ //谷歌
  preg_match( "|google.+q=([^\\&]*)|is", $referer, $tmp );
  $keyword = urldecode( $tmp[1] );
  $from = 'google';
 }elseif(strstr( $referer, 'so.com')){ //360搜索
  preg_match( "|so.+q=([^\\&]*)|is", $referer, $tmp );
  $keyword = urldecode( $tmp[1] );
  $from = '360'; 
 }elseif(strstr( $referer, 'sogou.com')){ //搜狗
  preg_match( "|sogou.com.+query=([^\\&]*)|is", $referer, $tmp );
  $keyword = urldecode( $tmp[1] );
  $from = 'sogou'; 
 }elseif(strstr( $referer, 'soso.com')){ //搜搜
  preg_match( "|soso.com.+w=([^\\&]*)|is", $referer, $tmp );
  $keyword = urldecode( $tmp[1] );
  $from = 'soso';
 }else {
  $keyword ='';
  $from = '';
 }
 return array('keyword'=>$keyword,'from'=>$from);
}
//以下为测试
//在搜索引擎搜索个关键词，进入网站
$word = search_word_from();
if(!empty($word['keyword'])){
 echo '关键字：'.$word['keyword'].' 来自：'.$word['from'];
}
?>