php生成xml文件问题（急）
请各位高手帮忙，下面的程序怎么样生成xml文件，以及怎么样读xml文件？
foreach ($forums as $k=>$v){
$sql = "SELECT * FROM ".$forum->_prefix.$forum->_table_name." WHERE parent_id = ".$v['forum_id']." ORDER BY post_cnt DESC LIMIT 0,6 ";
$forums[$k]['mobiles'] = $forum->_db->fetchAll($sql);
$j_data=($forums[$k]['mobiles']);
print_r($j_data);
 
foreach ($forums[$k]['mobiles'] as $s=>$t){
$prod_id = $t['prod_id'];
$sql = " SELECT count(prod_id) FROM ".$profileM->_prefix.$profileM->_table_name." WHERE prod_id = '".$prod_id."' GROUP BY prod_id ";
$forums[$k]['mobiles'][$s]['ucount'] = intval($profileM->_db->fetchOne($sql));
}
}

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烦请楼主把问题描述清楚，难道要让大家先猜你想干嘛。然后再帮你解决问题？
------解决方案--------------------
foreach