Sorting array?

gistfile1.php

$teste = array(
  array("foo" => "a", "bar" => "b", "timestamp" => 123456),
  array("foo" => "a", "bar" => "b", "timestamp" => 987654),
  array("foo" => "a", "bar" => "b", "timestamp" => 654789),
  array("foo" => "a", "bar" => "b", "timestamp" => 456123)
);

/*
 * how to transform that, in this (I mean, ordered by date)
 */
$teste = array(
  array("foo" => "a", "bar" => "b", "timestamp" => 123456),
  array("foo" => "a", "bar" => "b", "timestamp" => 456123),
  array("foo" => "a", "bar" => "b", "timestamp" => 654789),
  array("foo" => "a", "bar" => "b", "timestamp" => 987654)
);

//I don't want to do a sort by hand, but i can't find a function to do this

So, the solution by @alganet http://codepad.org/JibW94cM