i am trying to parse bing search xml but whenever i try to access xml element there is colon in every elemet

which gives error Parse error: syntax error, unexpected ':' in /

here is my php code

   foreach($searchresponse->web:Web->web:Results as $result) 
{ 
      printf(" \n%s", $result->web:Description); 
}     

here is bing xml response

<SearchResponse Version="2.2">
-
<Query>
 <SearchTerms>ipl</SearchTerms>
</Query>
-
<web:Web>
<web:Total>2430000</web:Total>
<web:Offset>0</web:Offset>
-
<web:Results> 
-
<web:WebResult>
<web:Title>Indian Premier League | IPLT20</web:Title>  

what is the meaning of colon in xml tags.