PHP如何動態為多維數組的子數組分別添加元素

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

function?addkey(&$val,?$key,?$param)

{

$val[$param['key']]?=?$param['val'];

}

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

print_r($a);