<?php

$array = array (1,4,2,1,6,4,9,7,2,9);
$unique = array();
foreach($array as $v)
  isset($k[$v]) || ($k[$v]=1) && $unique[] = $v; 

var_dump($unique);

array(6) {
  [0]=>
  int(1)
  [1]=>
  int(4)
  [2]=>
  int(2)
  [3]=>
  int(6)
  [4]=>
  int(9)
  [5]=>
  int(7)
}