多个foreach嵌套循环的问题

$xml = simplexml_load_file($xml_uri);$offer_url=array(					
"ItemCondition"					
=>"Qualifiers->ItemCondition",					
"ItemSubcondition"				
=>"Qualifiers->ItemSubcondition",					
"FulfillmentChannel"			
=>"Qualifiers->FulfillmentChannel",					
"ShipsDomestically"				
=>"Qualifiers->ShipsDomestically",					
"ShippingTime"					
=>"Qualifiers->ShippingTime->Max",					
"SellerPositiveFeedbackRating"	=>"Qualifiers->SellerPositiveFeedbackRating",					
"NumberOfOfferListingsConsidered"=>"NumberOfOfferListingsConsidered",					
"SellerFeedbackCount"			
=>"SellerFeedbackCount",					
"LandedPrice"					
=>"Price->LandedPrice->Amount",					
"ListingPrice"					
=>"Price->ListingPrice->Amount",					
"Shipping"						
=>"Price->Shipping->Amount",					
"MultipleOffersAtLowestPrice"	=>"MultipleOffersAtLowestPrice");
foreach($xml->GetLowestOfferListingsForASINResult->Product->LowestOfferListings->LowestOfferListing as $key){
foreach($offer_url as $name=>$value){
echo  $name."->".$key->$value."--------";
}
echo "<br>";
}  
}     
?>

$key->$value没有结果，请问应该怎么写？？

回复讨论(解决方案)

$name."->".$key->$value   
这样组装的是串，不是语句，不能被执行  
你需要适当的使用 eval 或 create_function 将其当做语句来执行

以下结果也是为空  

echo eval("\$key->\$value;");

请问语法有问题吗？

echo eval("return \$key->$value;");