Sander Bol

<?php
// First some SQL to execute
// You will only need the ALTER and UPDATE, the insert is to generate some example data so we can actually run tests on it.
/**
ALTER TABLE `test`.`feeds` ADD COLUMN `weight` SMALLINT NOT NULL DEFAULT 1  AFTER `url`;
INSERT INTO `feeds` (name, url)
VALUES
('Test 1', 'http://www.google.com/feeds'),
('Test 2', 'http://some-url.com'),
('Test 3', 'http://feeds-r-us.com'),
('Test 4', 'http://even-more-links.com'),
('Test 5', 'http://www.veryimportantfeed.com');
UPDATE `test`.`feeds` SET `weight`=1 WHERE `id`='1'
UPDATE `test`.`feeds` SET `weight`=1 WHERE `id`='2'
UPDATE `test`.`feeds` SET `weight`=1 WHERE `id`='3'
UPDATE `test`.`feeds` SET `weight`=1 WHERE `id`='4'
UPDATE `test`.`feeds` SET `weight`=6 WHERE `id`='5'
**/

function findRandomWeighted(array $items) {
   $maxWeight = 0;
   // Sum all the weights.
   foreach($items as $item) {
        $maxWeight += $item['weight'];
   }

   $index = rand(1, $maxWeight);
   foreach($items as $item) {
       $index -= $item['weight'];
       if($index <= 0) {
            return $item;
       }
   }
}

$conn = mysql_connect('localhost','username','password');
mysql_select_db('test', $conn);

$query = "SELECT * FROM `feeds`";

$result = mysql_query($query);
$data   = array();
while($output = mysql_fetch_assoc($result)) {
    $data[] = $output;
}

// Test
$selections = array(1=>0, 2=>0, 3=>0, 4=>0, 5=>0);
for($i = 0; $i < 1000; $i++) {
    $feed = findRandomWeighted($data);
    $selections[$feed['id']]++;
}

// Result should be approximately equal to the distribution of the weight.