用PHP简单地备份mysql数据库

<?php$dbname = "php100";$sqlfile = "";$mysqli= new mysqli("localhost","root","070423");$mysqli->select_db($dbname);//获取一个结果集对象，$tq = $mysqli->query("show tables from $dbname;");while($tr=$tq->fetch_row()){   $sqlfile .= get_table_fd($tr[0])."\n";   get_table_row($tr[0]);   }$f = fopen($dbname.".sql","w+");fwrite($f,$sqlfile);fclose($f);//获取表结构function get_table_fd($dbname){    global $mysqli;    $field = "create table `$dbname` (\n";    $query = $mysqli->query("select * from $dbname");    //fetch_field 返回结果集的下一个字段    //循环遍历出结果并赋予给左边的变量//     var_dump($query);    while($meta=$query->fetch_field()){        $field .= "`$meta->name` $meta->type($meta->max_length),\n";    }        $field .= ")";    return $field;}//获取表操作function get_table_row($dbname){    global $mysqli;    global $sqlfile;    $field = "";    $query = $mysqli->query("select * from $dbname");    while($row=$query->fetch_row()){        $field .= "insert into $dbname values('$row[0]','$row[1]','$row[2]') \n";            }        //以读写方式打开文件    $f=fopen($dbname.".sql","w+");    //写入文件    fwrite($f,$sqlfile);    fclose($f);}?>