<?php 
$arr = array(array(17,99), 
            array(45, 131),
            array(17,121),
            array(99,77),
            array(45, 51)

      );

 foreach($arr as $v)
  foreach($v as $m)
    $new_arr[] = $m;

  $array = array_chunk(array_unique($new_arr), 4);
  var_dump($array);

array(2) {
  [0]=>
  array(4) {
    [0]=>
    int(17)
    [1]=>
    int(99)
    [2]=>
    int(45)
    [3]=>
    int(131)
  }
  [1]=>
  array(3) {
    [0]=>
    int(121)
    [1]=>
    int(77)
    [2]=>
    int(51)
  }
}