php备份mysql的代码

<?php   
    $host="localhost";             
$user="root";          
$password="";            
$dbname="";          
mysql_connect($host,$user,$password);             
mysql_select_db($dbname);           
$mysql= "set charset utf8;rn";               
$q1=mysql_query("show tables");               
while($t=mysql_fetch_array($q1)){          
    $table=$t[0];          
    $q2=mysql_query("show create table `$table`");               
    $sql=mysql_fetch_array($q2);           
    $mysql.=$sql['Create Table'].";rnrn";           
         
    $q3=mysql_query("select * from `$table`");          
    while($data=mysql_fetch_assoc($q3)){          
        $keys=array_keys($data);          
        $keys=array_map('addslashes',$keys);          
        $keys=join('`,`',$keys);             
        $keys="`".$keys."`";            
        $vals=array_values($data);           
        $vals=array_map('addslashes',$vals);            
        $vals=join("','",$vals);           
        $vals="'".$vals."'";          
        $mysql.="insert into `$table`($keys) values($vals);rn";          
    }          
    $mysql.="rn";                       
}          
$filename=date('Ymj').".sql";             
$fp = fopen($filename,'w');             
fputs($fp,$mysql);               
fclose($fp);               
echo "数据备份成功,生成备份文件".$filename."";    
?>