函数生成唯一随机值数组

Question

As Mysql rand() is time consuming I am using alternate way using Mysql max() and PHP. I wrote this code for fetching random product_id's:

function RandomUniqueArray($min,$max,$limit){

    $random_array = array();
    if(isset($limit) && is_numeric($limit)){
        for($i=0;$i<$limit;){
            $rand_val = mt_rand($min, $max);
            if(!in_array($rand_val, $random_array)){
                $random_array[] = $rand_val;
                $i++;
            }
        }
    }
    return $random_array;
}

This works fine as I want each time it gives different result set with different unique values but it takes 6.232 micro seconds. Ohter I got by Google is:

$random_array = array_rand(array_fill($min,$max, true),$limit);

with takes only 0.101 microseconds but its result set is repeated means. Unique values array is fine but whole set is repeated. Why is it so???

I called both of these by one by one as

$random_array = RandomUniqueArray(1,64000,4);

And

$random_array = array_rand(array_fill(1,64000, true),4);

Thank you.

Answer 1

I made a script,that only takes ̣̣̣+- 4.5E-6.

Try it.

function randomValue($min,$max,$limit)
{
    $array = Array();
    $MAX = mt_rand($min,$max);
    for($i = 0;$i < $limit;$i++)
    {
        $array[$i] = mt_rand($min,$MAX);
        while( is_array($array[$i],$array) ) //To check if exist, if. Make new.
        {
           $array[$i] = mt_rand($min,$MAX);
        }
    }   
    return $array;
}