php 生成随机字符串不含aiove

srand((double)microtime()*1000000);//create a random number feed.
$ychar="0,1,2,3,4,5,6,7,8,9,B,C,D,F,G,H,J,K,L,M,N,P,Q,R,S,T,V,W,X,Y,Z";
$list=explode(",",$ychar);
for($i=0;$i<6;$i++){
$randnum=rand(0,35); // 10+26;
$authnum.=$list[$randnum];
}
echo authnum;