php往二维数组追加元素

$a=array(0=>array("name"=>"a","mail"=>"b"),1=>array("name"=>"d","mail"=>"e"),2=>array('name'=>'aaa','mail'=>'hhehe'));

function addkey(&$val, $key, $param)
{
    $val[$param['key']] = $param['val'];
}

array_walk($a,'addkey',array('key'=>'tel', 'val'=>'123'));
print_r($a);