So sieh das Script aus

        
            $myarray = array (
                array (
                    "timestamp" => 1,
                    "name"      => "foo",
                ),
                array (
                    "timestamp" => 4,
                    "name"      => "foobar",
                ),
                array (
                    "timestamp" => 3,
                    "name"      => "bar",
                ),
                array (
                    "timestamp" => 2,
                    "name"      => "batz",
                ),         
            );
            
            function cmp($a, $b) { 
            
                $t1 =  $a["timestamp"];
                $t2 =  $b["timestamp"];    
                return ($t1 < $t2)? -1 : (($t1 > $t2)? 1 : 0);
            }
        
            usort($myarray, "cmp");
        
        

... und das kömmt dabei raus:

Array
(
    [0] => Array
        (
            [timestamp] => 1
            [name] => foo
        )

    [1] => Array
        (
            [timestamp] => 2
            [name] => batz
        )

    [2] => Array
        (
            [timestamp] => 3
            [name] => bar
        )

    [3] => Array
        (
            [timestamp] => 4
            [name] => foobar
        )

)