Maximum secondary Key in a multidimensional array

[abdfahim]

I want to get the maximum values of the second key of a multidimensional array. Write now I am using the code below, which works. But interested to know whether anybody has any better idea?

 

$arr['a']['2012-08-04']=100;
    $arr['a']['2012-08-01']=4545;
    $arr['a']['2012-08-07']=2434;
    $arr['b']['2012-08-02']=2334;
    $arr['b']['2012-08-03']=2324;
    
    $dt=array();
    foreach($arr as $val){
$dt=array_merge($dt,$val);
    }
    echo max(array_keys($dt));

[Barand]

$max = '';
foreach ($arr as $k1=>$v1) {
    foreach ($v1 as $k=>$v) $max=max($max, $k);
}
echo $max.'<br />';