PHP XPATH within changing XML structure

I've an XML file like this:

<tr class="station">  
  <td class="realtime"> 
    <span>
      15:11 
    </span>
  </td> 
</tr>

<tr class="station">  
  <td class="clock"> 
    15:20 
  </td> 
</tr>

<tr class="station">  
  <td class="clock"> 
    15:30 
  </td> 
</tr>

<tr class="station">  
  <td class="realtime"> 
    <span>开发者_C百科
      15:41 
    </span>
  </td> 
</tr>

and I wanna parse it with xpath in php. The xml is been updated and parsed quite often.

I always want to get the first time (in this case 15:11)

The problem is that its not sure whether the surrounding tag is a td by class "clock" or "realtime".

If there is a so surrounding realtime, then there is a span tag within. Otherwise not.

In fact, its always the first "station"-class tag in which the information is, that matters. So is it possible to tell xpath to just evaluate within this tag?

Is there a good method for doing this in xpath?

(sry for my bad english)

In fact, its always the first "station"-class tag in which the information is, that matters. So is it possible to tell xpath to just evaluate within this tag?

With this wellformed input source:

<table>
    <tr class="station">
        <td class="realtime">
            <span>
                15:41
            </span>
        </td>
    </tr>
    <tr class="station">
        <td class="clock">
            15:20
        </td>
    </tr>
    <tr class="station">
        <td class="clock">
            15:30
        </td>
    </tr>
    <tr class="station">
        <td class="realtime">
            <span>
                15:41
            </span>
        </td>
    </tr>
</table>

This XPath expression:

/table/tr[@class='station'][1]/td

Note: Just select the element you want and use the proper DOM API method to get the string value. It doesn't matter whether there is a span element or not.

If you want to...

/table/tr[@class='station'][1]/td//text()