PhP比較字符串相似度

[PHP]代碼

<?php 
require('conn.php');
$sql="select title from content order by id desc limit 20"; //判斷標題相似度
$result=mysql_query($sql,$conn);
$cf=0;
while($row=mysql_fetch_array($result)){
similar_text($row['title'], $title, $percent); //比較相似度 存放于$percent
if($percent>90){$cf=1;break;} //飄易注:相似度高于90% 則判斷重復
}
if($cf==1){
echo "<SCRIPT language=JavaScript>alert('抱歉！禁止發布重復信息！');";
echo "this.location.href='vbscript:history.back()';</SCRIPT>";
mysql_close();
exit();
}
?>