public function idf($input, Zend_Search_Lucene_Interface $reader)
    {
        if (!is_array($input)) {
            return $this->idfFreq($reader->docFreq($input), $reader->count());
        } else {
            $idf = 0.0;
            foreach ($input as $term) {
                $idf += $this->idfFreq($reader->docFreq($term), $reader->count());
            }
            return $idf;
        }
    }
public function idf($input, Zend_Search_Lucene_Interface $reader)
    {
        if (!is_array($input)) {
            return $this->idfFreq($reader->docFreq($input), $reader->count());
        } else {
            $idf = 0.0;
            foreach ($input as $term) {
                $idf += $this->idfFreq($reader->docFreq($term), $reader->count());
            }
            return $idf;
        }
    }
public function idf ( $ input , Zend_Search_Lucene_Interface $ reader ) { if ( ! is_array ( $ input ) ) { return $ this -> idfFreq ( $ reader -> docFreq ( $ input ) , $ reader -> count ( ) ) ; } else { $ idf = 0.0 ; foreach ( $ input as $ term ) { $ idf += $ this -> idfFreq ( $ reader -> docFreq ( $ term ) , $ reader -> count ( ) ) ; } return $ idf ; } }
Computes a score factor for a simple term or a phrase.

The default implementation is:
return idfFreq(searcher.docFreq(term), searcher.maxDoc());

input - the term in question or array of terms
reader - reader the document collection being searched
Returns a score factor for the term

@param  mixed                        $input
@param  Zend_Search_Lucene_Interface $reader
@return a score factor for the term
Computes a score factor for a simple term or a phrase .