<?php
/*** 一致性Hash分布* 天涯PHP博客* http://blog.phpha.com*/
class FlexiHash{//服务器列表private $serverList = array();//记录是否已经排序private $isSorted = FALSE;//添加一台服务器public function addServer($server){$hash = $this->mHash($server);if(!isset($this->serverList[$hash])){$this->serverList[$hash] = $server;}//需要重新排序$this->isSorted = FALSE;return TRUE;}//移除一台服务器public function removeServer($server){$hash = $this->mHash($server);if(isset($this->serverList[$hash])){unset($this->serverList[$hash]);}//需要重新排序$this->isSorted = FALSE;return TRUE;}//在当前服务器列表查找合适的服务器public function lookup($key){$hash = $this->mHash($key);//先进行倒序排序操作if(!$this->isSorted){krsort($this->serverList, SORT_NUMERIC);$this->isSorted = TRUE;}//圆环上顺时针方向查找当前KEY紧邻的一台服务器foreach($this->serverList as $pos => $server){if($hash >= $pos)  return $server;}//没有找到则返回顺时针方向最后一台服务器return $this->serverList[count($this->serverList) - 1];}//Hash函数private function mHash($key){$md5 = substr(md5($key), 0, 8);$seed = 31;$hash = 0;for($i = 0; $i < 8; $i++){$hash = $hash * $seed + ord($md5{$i});$i++;}return $hash & 0x7FFFFFFF;}
}
?>

<?php
/*** 一致性Hash分布测试代码* 天涯PHP博客* http://blog.phpha.com*/
$hserver = new FlexiHash();
//初始5台服务器
$hserver->addServer("192.168.1.1");
$hserver->addServer("192.168.1.2");
$hserver->addServer("192.168.1.3");
$hserver->addServer("192.168.1.4");
$hserver->addServer("192.168.1.5");
echo "save key1 in server: ", $hserver->lookup('key1'), "<br/>";
echo "save key2 in server: ", $hserver->lookup('key2'), "<br/>";
echo '===============================================<br/>';
//移除1台服务器
$hserver->removeServer("192.168.1.4");
echo "save key1 in server: ", $hserver->lookup('key1'), "<br/>";
echo "save key2 in server: ", $hserver->lookup('key2'), "<br/>";
echo '===============================================<br/>';
//添加1台服务器
$hserver->addServer('192.168.1.6');
echo "save key1 in server: ", $hserver->lookup('key1'), "<br/>";
echo "save key2 in server: ", $hserver->lookup('key2');
?>

//测试结果如下：
save key1 in server: 192.168.1.4
save key2 in server: 192.168.1.2
==================================
save key1 in server: 192.168.1.3
save key2 in server: 192.168.1.2
==================================
save key1 in server: 192.168.1.3
save key2 in server: 192.168.1.2