The xml i'm working on looks like this:

```
     <item>
     <title>$39.99 and Under Juniors' Swimwear</title>
     <link>http://www.amazon.com/s/ref=xs_gb_rss_A1RFRNENBWTVO4/?rh=n:1036592,n:!2334084011,n:!2334146011,n:8021415011,p_6:ATVPDKIKX0DER&amp;bbn=8021415011&amp;ie=UTF8&amp;qid=1398271335&amp;rnid=15683531&amp;ccmID=380205&amp;tag=bugash-20</link>
     <description>&lt;table&gt;&lt;tr&gt;&lt;td&gt;&lt;a rel="nofollow" target="_blank" href="http://www.amazon.com/s/ref=xs_gb_rss_A1RFRNENBWTVO4/?rh=n:1036592,n:!2334084011,n:!2334146011,n:8021415011,p_6:ATVPDKIKX0DER&amp;bbn=8021415011&amp;ie=UTF8&amp;qid=1398271335&amp;rnid=15683531&amp;ccmID=380205&amp;tag=rssfeeds-20"&gt;&lt;img src="http://ecx.images-amazon.com/images/I/31kwUz5PiZL._SL160_.jpg" alt="Product Image" style='border:0;'/&gt;&lt;/a&gt;&lt;/td&gt;&lt;td&gt;&lt;tr&gt;&lt;td&gt;$39.99 and Under Juniors' Swimwear&lt;/td&gt;&lt;/tr&gt;&lt;tr&gt;&lt;td&gt;Expires May 10, 2014&lt;/td&gt;&lt;/tr&gt;&lt;/tr&gt;&lt;/table&gt;</description>
     <guid isPermaLink="false">http://promotions.amazon.com/gp/goldbox/5159412---5opWoFoLiIfWceLGIhXzm2wwCMk=</guid>
     <pubDate>Sat, 26 Apr 2014 07:00:00 +0000</pubDate>
  </item>

```

i want to extract just the 'img src' field from the 'description' tag.how do i do that in php.?