xml转json,怎么筛选数据？

Question

下边的xml，想转为json
但P节点下只需要<PN><PT>这两个节点的数据，其他数据不需要。
如果直接用json_encode转出来，是所有的数据
请问怎么能转为json,但只要<PN><PT>的数据，怎么弄？例如
{"PN":"\u7b2c\u4e00\u5468\u64ad\u5267\u573a\uff1a\u8ffd\u9c7c\u4f20\u5947 31","PT":"2013-08-19 22:01:00"}-------xml---------
<Root>  <P>
    <id>110171675</id>
    <PN>张三</PN>
    <PT>2013-08-19 00:02:00</PT>
    <Cd>46</Cd>
    <Td>24</Td>
    <Fd>74750</Fd>
    <Fd2>0</Fd2>
    <cPT>2013-08-19 00:02:00</cPT>
    <AMPM>AM</AMPM>
    <ls/>
  </P>
  <P>
    <id>110171676</id>
    <PN>我是大美人</PN>
    <PT>2013-08-19 01:15:00</PT>
    <Cd>46</Cd>
    <Td>24</Td>
    <Fd>74501</Fd>
    <Fd2>0</Fd2>
    <cPT>2013-08-19 01:15:00</cPT>
    <AMPM>AM</AMPM>
    <ls/>
  </P>
  <P>
    <id>110171677</id>
    <PN>李四</PN>
    <PT>2013-08-19 02:09:00</PT>
    <Cd>46</Cd>
    <Td>24</Td>
    <Fd>64519</Fd>
    <Fd2>71411</Fd2>
    <cPT>2013-08-19 02:09:00</cPT>
    <AMPM>AM</AMPM>
    <ls/>
  </P>  
</Root>
JSONXML

Answer 1

$string = <<<XML
<Root>
  <P>
    <id>110171675</id>
    <PN>张三</PN>
    <PT>2013-08-19 00:02:00</PT>
    <Cd>46</Cd>
    <Td>24</Td>
    <Fd>74750</Fd>
    <Fd2>0</Fd2>
    <cPT>2013-08-19 00:02:00</cPT>
    <AMPM>AM</AMPM>
    <ls/>
  </P>
  <P>
    <id>110171676</id>
    <PN>我是大美人</PN>
    <PT>2013-08-19 01:15:00</PT>
    <Cd>46</Cd>
    <Td>24</Td>
    <Fd>74501</Fd>
    <Fd2>0</Fd2>
    <cPT>2013-08-19 01:15:00</cPT>
    <AMPM>AM</AMPM>
    <ls/>
  </P>
  <P>
    <id>110171677</id>
    <PN>李四</PN>
    <PT>2013-08-19 02:09:00</PT>
    <Cd>46</Cd>
    <Td>24</Td>
    <Fd>64519</Fd>
    <Fd2>71411</Fd2>
    <cPT>2013-08-19 02:09:00</cPT>
    <AMPM>AM</AMPM>
    <ls/>
  </P>  
</Root>
XML;$xml = simplexml_load_string($string);foreach($xml->P as $item){
     $item=(array)$item;
    $arr[]=array('PN'=>$item['PN'],'PT'=>$item['PT']);
}
echo json_encode($arr);
[{"PN":"\u5f20\u4e09","PT":"2013-08-19 00:02:00"},{"PN":"\u6211\u662f\u5927\u7f8e\u4eba","PT":"2013-08-19 01:15:00"},{"PN":"\u674e\u56db","PT":"2013-08-19 02:09:00"}]

Answer 2

$xml =<<< XML
<Root>
  <P>
    <id>110171675</id>
    <PN>张三</PN>
    <PT>2013-08-19 00:02:00</PT>
    <Cd>46</Cd>
    <Td>24</Td>
    <Fd>74750</Fd>
    <Fd2>0</Fd2>
    <cPT>2013-08-19 00:02:00</cPT>
    <AMPM>AM</AMPM>
    <ls/>
  </P>
  <P>
    <id>110171676</id>
    <PN>我是大美人</PN>
    <PT>2013-08-19 01:15:00</PT>
    <Cd>46</Cd>
    <Td>24</Td>
    <Fd>74501</Fd>
    <Fd2>0</Fd2>
    <cPT>2013-08-19 01:15:00</cPT>
    <AMPM>AM</AMPM>
    <ls/>
  </P>
  <P>
    <id>110171677</id>
    <PN>李四</PN>
    <PT>2013-08-19 02:09:00</PT>
    <Cd>46</Cd>
    <Td>24</Td>
    <Fd>64519</Fd>
    <Fd2>71411</Fd2>
    <cPT>2013-08-19 02:09:00</cPT>
    <AMPM>AM</AMPM>
    <ls/>
  </P>  
</Root>
XML;
$sm = simplexml_load_string($xml);
foreach($sm->P as $item) {
  $r[] = array('PN' => strval($item->PN), 'PT' => strval($item->PT));
}
echo json_encode($r);[{"PN":"\u5f20\u4e09","PT":"2013-08-19 00:02:00"},{"PN":"\u6211\u662f\u5927\u7f8e\u4eba","PT":"2013-08-19 01:15:00"},{"PN":"\u674e\u56db","PT":"2013-08-19 02:09:00"}]