Index: src/java/org/apache/lucene/search/payloads/AveragePayloadFunction.java
===================================================================
--- src/java/org/apache/lucene/search/payloads/AveragePayloadFunction.java	(revision 911598)
+++ src/java/org/apache/lucene/search/payloads/AveragePayloadFunction.java	(working copy)
@@ -1,5 +1,7 @@
 package org.apache.lucene.search.payloads;
 
+import org.apache.lucene.search.Explanation;
+
 /**
  * Licensed to the Apache Software Foundation (ASF) under one or more
  * contributor license agreements.  See the NOTICE file distributed with
@@ -25,6 +27,8 @@
  *
  **/
 public class AveragePayloadFunction extends PayloadFunction{
+	int numPayloadsSeen=0;
+	float payloadScore=0;
 
   @Override
   public float currentScore(int docId, String field, int start, int end, int numPayloadsSeen, float currentScore, float currentPayloadScore) {
@@ -33,8 +37,19 @@
 
   @Override
   public float docScore(int docId, String field, int numPayloadsSeen, float payloadScore) {
+	this.numPayloadsSeen = numPayloadsSeen;
+	this.payloadScore = payloadScore;
     return numPayloadsSeen > 0 ? (payloadScore / numPayloadsSeen) : 1;
   }
+  
+  @Override
+  public Explanation explain(int doc) {
+      Explanation payloadBoost = new Explanation();
+      float avgPayloadScore = (numPayloadsSeen > 0 ? (payloadScore / numPayloadsSeen) : 1);
+      payloadBoost.setValue(avgPayloadScore);
+      payloadBoost.setDescription("AveragePayloadFunction(...)");
+      return payloadBoost;
+  } 
 
   @Override
   public int hashCode() {
Index: src/java/org/apache/lucene/search/payloads/MaxPayloadFunction.java
===================================================================
--- src/java/org/apache/lucene/search/payloads/MaxPayloadFunction.java	(revision 911598)
+++ src/java/org/apache/lucene/search/payloads/MaxPayloadFunction.java	(working copy)
@@ -1,5 +1,7 @@
 package org.apache.lucene.search.payloads;
 
+import org.apache.lucene.search.Explanation;
+
 /**
  * Licensed to the Apache Software Foundation (ASF) under one or more
  * contributor license agreements.  See the NOTICE file distributed with
@@ -25,21 +27,33 @@
  *
  **/
 public class MaxPayloadFunction extends PayloadFunction {
+    int numPayloadsSeen=0;
+    float payloadScore=0;	
+   
   @Override
-  public float currentScore(int docId, String field, int start, int end, int numPayloadsSeen, float currentScore, float currentPayloadScore) {
-    if (numPayloadsSeen == 0) {
-      return currentPayloadScore;
-    } else {
-      return Math.max(currentPayloadScore, currentScore);
+    public float currentScore(int docId, String field, int start, int end, int numPayloadsSeen, float currentScore, float currentPayloadScore) {
+    	if (numPayloadsSeen == 0) {
+    		return currentPayloadScore;
+    	} else {
+    		return Math.max(currentPayloadScore, currentScore);
+    	}
     }
-  }
 
-  @Override
+  @Override    
   public float docScore(int docId, String field, int numPayloadsSeen, float payloadScore) {
-    return numPayloadsSeen > 0 ? payloadScore : 1;
+	this.numPayloadsSeen = numPayloadsSeen;
+	this.payloadScore = payloadScore;	  
+	return numPayloadsSeen > 0 ? payloadScore : 1;
+  }
+  @Override    
+  public Explanation explain(int doc) {
+    Explanation payloadBoost = new Explanation();
+    float maxPayloadScore = (numPayloadsSeen > 0 ? payloadScore : 1);
+    payloadBoost.setValue(maxPayloadScore);
+    payloadBoost.setDescription("MaxPayloadFunction(...)");
+    return payloadBoost;
   }
-  
-  @Override
+  @Override    
   public int hashCode() {
     final int prime = 31;
     int result = 1;
@@ -46,7 +60,6 @@
     result = prime * result + this.getClass().hashCode();
     return result;
   }
-
   @Override
   public boolean equals(Object obj) {
     if (this == obj)
Index: src/java/org/apache/lucene/search/payloads/MinPayloadFunction.java
===================================================================
--- src/java/org/apache/lucene/search/payloads/MinPayloadFunction.java	(revision 911598)
+++ src/java/org/apache/lucene/search/payloads/MinPayloadFunction.java	(working copy)
@@ -1,5 +1,7 @@
 package org.apache.lucene.search.payloads;
 
+import org.apache.lucene.search.Explanation;
+
 /**
  * Licensed to the Apache Software Foundation (ASF) under one or more
  * contributor license agreements.  See the NOTICE file distributed with
@@ -22,22 +24,32 @@
  *
  **/
 public class MinPayloadFunction extends PayloadFunction {
+    int numPayloadsSeen=0;
+    float payloadScore=0;	
 
   @Override
-  public float currentScore(int docId, String field, int start, int end, int numPayloadsSeen, float currentScore, float currentPayloadScore) {
-    if (numPayloadsSeen == 0) {
-      return currentPayloadScore;
-    } else {
-      return Math.min(currentPayloadScore, currentScore);
+    public float currentScore(int docId, String field, int start, int end, int numPayloadsSeen, float currentScore, float currentPayloadScore) {
+    	if (numPayloadsSeen == 0) {
+    		return currentPayloadScore;
+    	} else {
+    		return Math.min(currentPayloadScore, currentScore);
+    	}
     }
-  }
 
   @Override
   public float docScore(int docId, String field, int numPayloadsSeen, float payloadScore) {
+    this.numPayloadsSeen = numPayloadsSeen;
+    this.payloadScore = payloadScore;		  
     return numPayloadsSeen > 0 ? payloadScore : 1;
   }
-  
   @Override
+  public Explanation explain(int doc) {
+	Explanation payloadBoost = new Explanation();
+	float maxPayloadScore = (numPayloadsSeen > 0 ? payloadScore : 1);
+	payloadBoost.setValue(maxPayloadScore);
+	payloadBoost.setDescription("MinPayloadFunction(...)");
+	return payloadBoost;
+  }  
   public int hashCode() {
     final int prime = 31;
     int result = 1;
Index: src/java/org/apache/lucene/search/payloads/PayloadFunction.java
===================================================================
--- src/java/org/apache/lucene/search/payloads/PayloadFunction.java	(revision 911598)
+++ src/java/org/apache/lucene/search/payloads/PayloadFunction.java	(working copy)
@@ -17,6 +17,7 @@
  */
 
 import java.io.Serializable;
+import org.apache.lucene.search.Explanation;
 
 /**
  * An abstract class that defines a way for Payload*Query instances to transform
@@ -21,12 +22,12 @@
 /**
  * An abstract class that defines a way for Payload*Query instances to transform
  * the cumulative effects of payload scores for a document.
- * 
+ *
  * @see org.apache.lucene.search.payloads.PayloadTermQuery for more information
- * 
+ *
  * @lucene.experimental This class and its derivations are experimental and subject to
  *               change
- * 
+ *
  **/
 public abstract class PayloadFunction implements Serializable {
 
@@ -55,6 +56,14 @@
    */
   public abstract float docScore(int docId, String field, int numPayloadsSeen, float payloadScore);
   
+  
+  public Explanation explain(int docId){
+	  Explanation result = new Explanation();
+	  result.setDescription("Unimpl Payload Function Explain");
+	  result.setValue(1);
+	  return result;
+  };
+  
   @Override
   public abstract int hashCode();
   
Index: src/java/org/apache/lucene/search/payloads/PayloadNearQuery.java
===================================================================
--- src/java/org/apache/lucene/search/payloads/PayloadNearQuery.java	(revision 911598)
+++ src/java/org/apache/lucene/search/payloads/PayloadNearQuery.java	(working copy)
@@ -79,7 +79,7 @@
       newClauses[i] = (SpanQuery) clauses.get(i).clone();
     }
     PayloadNearQuery boostingNearQuery = new PayloadNearQuery(newClauses, slop,
-        inOrder);
+        inOrder, function);
     boostingNearQuery.setBoost(getBoost());
     return boostingNearQuery;
   }
@@ -84,7 +84,6 @@
     return boostingNearQuery;
   }
 
-  @Override
   public String toString(String field) {
     StringBuilder buffer = new StringBuilder();
     buffer.append("payloadNear([");
@@ -152,7 +151,6 @@
 
   public class PayloadNearSpanScorer extends SpanScorer {
     Spans spans;
-
     protected float payloadScore;
     private int payloadsSeen;
     Similarity similarity = getSimilarity();
@@ -204,15 +202,22 @@
     //
     @Override
     protected boolean setFreqCurrentDoc() throws IOException {
-      if (!more) {
-        return false;
-      }
-      Spans[] spansArr = new Spans[1];
-      spansArr[0] = spans;
-      payloadScore = 0;
-      payloadsSeen = 0;
-      getPayloads(spansArr);
-      return super.setFreqCurrentDoc();
+        if (!more) {
+            return false;
+          }
+          doc = spans.doc();
+          freq = 0.0f;
+          payloadScore = 0;
+          payloadsSeen = 0;
+          do {
+            int matchLength = spans.end() - spans.start();
+            freq += getSimilarity().sloppyFreq(matchLength);
+            Spans[] spansArr = new Spans[1];
+            spansArr[0] = spans;
+            getPayloads(spansArr);            
+            more = spans.next();
+          } while (more && (doc == spans.doc()));
+          return true;    	
     }
 
     @Override
@@ -225,16 +230,14 @@
     @Override
     protected Explanation explain(int doc) throws IOException {
       Explanation result = new Explanation();
+      // Add detail about tf/idf...
       Explanation nonPayloadExpl = super.explain(doc);
       result.addDetail(nonPayloadExpl);
-      Explanation payloadBoost = new Explanation();
-      result.addDetail(payloadBoost);
-      float avgPayloadScore = (payloadsSeen > 0 ? (payloadScore / payloadsSeen)
-          : 1);
-      payloadBoost.setValue(avgPayloadScore);
-      payloadBoost.setDescription("scorePayload(...)");
-      result.setValue(nonPayloadExpl.getValue() * avgPayloadScore);
-      result.setDescription("bnq, product of:");
+      // Add detail about payload
+      Explanation payloadExpl = function.explain(doc);
+      result.addDetail(payloadExpl);
+      result.setValue(nonPayloadExpl.getValue() * payloadExpl.getValue());
+      result.setDescription("PayloadNearQuery, product of:");
       return result;
     }
   }