Amazon Product API：设置多个关键字

I am using ApaiIO API for PHP and I am using following code to pull item list but it is not pulling items. When I put either hadoop or Java it fetches then.

$apaiIO = new ApaiIO($conf);

$search = new Search();
$search->setCategory('Books');
$search->setCondition('All');
$search->setKeywords('Hadoop Java');

the query is an intersection, not an union

it does not retryeve "any of hadoop and java" but items with "both hadoop and java", maybe none

I solved a similar situation by merging the results of 2 queryes:

function searchAmazon($keywords){
..... //preamble code
$apaiIO = new ApaiIO($conf);

$search = new Search();
... //setting and filters
$search->setKeywords($keywords);
... //retrieve it and put it in an array or similar    
... //blabla return
}


$products1=searchAmazon($keyword1);

$products2=searchAmazon($keyword2);

$products=merge($products1,$products2);//use some merge algorithm of your choice