php语句，怎么从数据库中随机获取数据字段。

if(!$con = mysql_connect("localhost","root","root")){die(mysql_error())}

mysql_select_db("ali_xt")

mysql_query('set names utf8')

//找出ali_admin表的字段

$res = mysql_query('show columns from ali_admin')

//将数据给弄出来

$data = array()

while ($row = mysql_fetch_assoc($res, MYSQL_NUM)) {

$data[] = $row

}

//随机个数，默认5

$rand_times = 5

$rand_times = count($data)<$rand_times?count($data):$rand_times

$result = array()

for( $i=0$i<$rand_times$i++ ){

$result[] = $data[rand(0,count($data)-1)][0]

}

echo "<pre>"

print_r($result) //输出5个随机字段

mysql_close($con)

//纯手写的，不明白可以问我，记得给分

去掉foreach

$sql="select * from phome_ecms_wma order by rand() limit 30"

就行了