$array = array(array(100,5),array(5,5),array(100,20));
function exNm($one, $two){
$new='';
$scope=0;
for($i=1;$i<=$two;$i++){
$mx = ($one-$scope)-($two-$i);
$rnd = ($i==$two ? $mx : rand(1,$mx));

$scope+=$rnd;
$new[] = $rnd;
}
shuffle($new);
return implode('<br>',$new).'<br>('.array_sum($new).')';
}
foreach($array as $q){
echo 'Данные: '.$q[0].' и '.$q[1].'<br>';
echo exNm($q[0],$q[1]);
echo '<br><br>';
}