Generating random results by weight in PHP?

Question

I know how to generate a random number in PHP but lets say I want a random number between 1-10 but I want more 3,4,5\'s then 8,9,10\'s. How is this possible? I would post wh

Answer 1

Plain and fair. Just copy/paste and test it.

/**
 * Return weighted probability
 * @param (array) prob=>item 
 * @return key
 */
function weightedRand($stream) {
    $pos = mt_rand(1,array_sum(array_keys($stream)));           
    $em = 0;
    foreach ($stream as $k => $v) {
        $em += $k;
        if ($em >= $pos)
            return $v;
    }

}

$item['30'] = 'I have more chances than everybody :]';
$item['10'] = 'I have good chances';
$item['1'] = 'I\'m difficult to appear...';

for ($i = 1; $i <= 10; $i++) {
    echo weightedRand($item).'
';
}

Edit: Added missing bracket at the end.