php 广告点击统计代码(php+mysql)

CREATE TABLE IF NOT EXISTS `ad_count` (
`ad_id` int(8) NOT NULL auto_increment,
`ad_hit` int(8) NOT NULL default '0',
`ad_name` varchar(200) character set gb2312 default NULL,
`ad_datetime` datetime default NULL,
`ad_qq` varchar(15) character set gb2312 default NULL,
`ad_url` varchar(900) character set gb2312 NOT NULL,
`ad_price` int(8) NOT NULL,
PRIMARY KEY (`ad_id`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1 AUTO_INCREMENT=4 ;

?php
 require_once("......省了");
 $ad_id =get_value('ad_id','');这里下面有讲
 if(is_numeric( $ad_id ) ){
 
  $ad_select="select ad_id,ad_url from ad_count where ad_id='$ad_id' limit 1";  
  $ad_update="Update ad_count set ad_hit=ad_hit+1 where ad_id='$ad_id' limit 1";
  
  $ad_result=mysql_query($ad_select) or die('id error');
  
   if( mysql_num_rows( $ad_result) ){   
    mysql_query($ad_update);    
    $ad_rs=mysql_fetch_array($ad_result);    
    header("location:".$ad_rs['ad_url']);    
    mysql_free_result($ad_rs);       
   }
 }

function htmltohtml($Str){
 $temp =str_replace(chr(13),'br/>',$Str);
 $temp =str_replace('','lt;',$Str);
 $temp =str_replace('>','gt;',$Str);
 $temp =addslashes($Str);
 return $temp;
 }
 function get_value($value,$para){ 
 return htmltohtml(empty($para)?(isset($_GET[$value])?$_GET[$value]:''):(isset($_POST[$value])?$_POST[$value]:''));
 }