How to do random with priority? [duplicate]

Question

This is my code, for example:

<?php
     $arr = array(
          array("url" => "http://google.com", "priority" => 2),
          array("url" => "http://facebook.com", "priority" => 2),
          array("url" => "http://youtube.com", "priority" => 2),
          array("url" => "http://stackoverflow.com", "priority" => 1),
          array("url" => "http://kickass.to", "priority" => 1),
          array("url" => "http://twitter.com", "priority" => 1),
          array("url" => "http://example.com", "priority" => 1),
     );
?>

I want the system to randomly display one of the url's on each refresh. I want it to display the higher priority more times than the lower. I need it for banner system, and the ones with higher priority paying more, so they should be seen more.

How to do it?

Answer 1

You can add items to an array based on their priority. If an item has a priority of 2, you can add it to the array twice. Then you can pull out a random item from the array.

// CREATE A NEW ARRAY TO HOLD ALL OF THE BANNERS
$banner_array = array();     

// LOOP THROUGH EACH ITEM IN THE ARRAY CURRENTLY HOLDING THE BANNERS
foreach ($arr AS $banner) {

    // FOR EACH NUMBER IN THE PRIORITY, ADD THE ITEM TO OUR NEW ARRAY
    // google.com, facebook.com, youtube.com WILL BE ADDED IN TWICE
    for ($i = 0; $i < $banner['priority']; $i++) {
        $banner_array[] = $banner['url'];
    }
}

// COUNT THE TOTAL NUMBER OF ITEMS IN OUR ARRAY
// WE WILL PICK OUT A NUMBER BETWEEN ZERO AND THIS NUMBER (MINUS 1)
$item_count = count($banner_array) - 1;

// ONCE WE HAVE A RANDOM NUMBER, WE CAN ACCESS THAT ITEM OF THE ARRAY
print "RANDOM URL: ".$banner_array[get_random_item($item_count)];


// THIS FUNCTION PICKS A NUMBER BETWEEN ZERO AND THE NUMBER OF ITEMS IN OUR ARRAY
function get_random_item($item_count) {
    mt_srand(microtime() * 1000000);
    $random_number = rand(0, $item_count);
    return $random_number;
}

Answer 2

Iterate over all the banners, and assign a key (numeral id) for each. To those with a higher priority, assign 2 keys (or more if you wish an even higher priority). Then just find the random number between 0 (assuming it's zero-based) and the total number of keys:

rand(0, count($keys) - 1);

---

UPDATE

Here is some code:

// $arr = Your original array

$keys = array();
for ($i = 0; $i < count($arr); $i++) { // you can also use foreach here
     for ($u = 0; $u < $arr[$i]['priority']; $u++) {
         $keys[] = $i;      
     }
}

Then, to fetch a random url, but with priorities, do this:

$arr[ $keys[ rand(0, count($keys) - 1) ] ];