php 随机取数组中的一个值，或多个值

function rand_one($numone = array()){
$len = sizeof($numone,1);
$j = rand(0,$len-1);    

    return $numone[$j];    

}

function rand_num($num = array(),$sj = 5){
$myWant = array();
for($i=0;$i<$sj;$i++){
 $len = sizeof($num,1);
 $keys = array_keys($num);
 $j = rand_one($keys);
 
 $myWant[] = $num[$j];
 
 unset($num[$j]);
}
return $myWant;

}