Index: test/unit/ajax.js
===================================================================
--- test/unit/ajax.js	(revision 6581)
+++ test/unit/ajax.js	(working copy)
@@ -251,11 +251,34 @@
 });
 
 test("jQuery.param()", function() {
-	expect(8);
+	expect(13);
+	
+  equals( jQuery.param.traditional, undefined, "traditional flag, undefined by default" );
+  
 	var params = {foo:"bar", baz:42, quux:"All your base are belong to us"};
 	equals( jQuery.param(params), "foo=bar&baz=42&quux=All+your+base+are+belong+to+us", "simple" );
 
 	params = {someName: [1, 2, 3], regularThing: "blah" };
+	equals( jQuery.param(params), "someName%5B%5D=1&someName%5B%5D=2&someName%5B%5D=3&regularThing=blah", "with array" );
+
+	params = {foo: ['a', 'b', 'c']};
+	equals( jQuery.param(params), "foo%5B%5D=a&foo%5B%5D=b&foo%5B%5D=c", "with array of strings" );
+
+	params = {foo: ["baz", 42, "All your base are belong to us"] };
+	equals( jQuery.param(params), "foo%5B%5D=baz&foo%5B%5D=42&foo%5B%5D=All+your+base+are+belong+to+us", "more array" );
+
+	params = {foo: { bar: 'baz', beep: 42, quux: 'All your base are belong to us' } };
+	equals( jQuery.param(params), "foo%5Bbar%5D=baz&foo%5Bbeep%5D=42&foo%5Bquux%5D=All+your+base+are+belong+to+us", "even more arrays" );
+	
+	params = { a:[1,2], b:{ c:3, d:[4,5], e:{ x:[6], y:7, z:[8,9] }, f:true, g:false, h:undefined }, i:[10,11], j:true, k:false, l:[undefined,0], m:"cowboy hat?" };
+	equals( jQuery.param(params), "a%5B%5D=1&a%5B%5D=2&b%5Bc%5D=3&b%5Bd%5D%5B%5D=4&b%5Bd%5D%5B%5D=5&b%5Be%5D%5Bx%5D%5B%5D=6&b%5Be%5D%5By%5D=7&b%5Be%5D%5Bz%5D%5B%5D=8&b%5Be%5D%5Bz%5D%5B%5D=9&b%5Bf%5D=true&b%5Bg%5D=false&b%5Bh%5D=undefined&i%5B%5D=10&i%5B%5D=11&j=true&k=false&l%5B%5D=undefined&l%5B%5D=0&m=cowboy+hat%3F", "huge structure" );
+	
+	jQuery.param.traditional = true;
+	
+	var params = {foo:"bar", baz:42, quux:"All your base are belong to us"};
+	equals( jQuery.param(params), "foo=bar&baz=42&quux=All+your+base+are+belong+to+us", "simple" );
+
+	params = {someName: [1, 2, 3], regularThing: "blah" };
 	equals( jQuery.param(params), "someName=1&someName=2&someName=3&regularThing=blah", "with array" );
 
 	params = {foo: ['a', 'b', 'c']};
@@ -266,16 +289,10 @@
 
 	params = {"foo[bar]":"baz", "foo[beep]":42, "foo[quux]":"All your base are belong to us"};
 	equals( jQuery.param(params), "foo%5Bbar%5D=baz&foo%5Bbeep%5D=42&foo%5Bquux%5D=All+your+base+are+belong+to+us", "even more arrays" );
+	
+	params = { a:[1,2], b:{ c:3, d:[4,5], e:{ x:[6], y:7, z:[8,9] }, f:true, g:false, h:undefined }, i:[10,11], j:true, k:false, l:[undefined,0], m:"cowboy hat?" };
+	equals( jQuery.param(params), "a=1&a=2&b=%5Bobject+Object%5D&i=10&i=11&j=true&k=false&l=undefined&l=0&m=cowboy+hat%3F", "huge structure" );
 
-	params = {foo: {bar: "baz", beep: 42, quux: "All your base are belong to us"}};
-	equals( jQuery.param(params), "foo%5Bbar%5D=baz&foo%5Bbeep%5D=42&foo%5Bquux%5D=All+your+base+are+belong+to+us", "nested object" );
-
-	params = {foo: {"bar[]": [1,2,3]}};
-	equals( jQuery.param(params), "foo%5Bbar%5D%5B%5D=1&foo%5Bbar%5D%5B%5D=2&foo%5Bbar%5D%5B%5D=3", "nested array");
-
-	params = {foo: [{bar: "baz", beep: 42}, {bar: "baz2", beep: 43}]};
-	equals( jQuery.param(params), "foo%5Bbar%5D=baz&foo%5Bbeep%5D=42&foo%5Bbar%5D=baz2&foo%5Bbeep%5D=43", "nested array of objects" );
-
 });
 
 test("synchronous request", function() {
Index: src/ajax.js
===================================================================
--- src/ajax.js	(revision 6581)
+++ src/ajax.js	(working copy)
@@ -585,39 +585,52 @@
 	// Serialize an array of form elements or a set of
 	// key/values into a query string
 	param: function( a ) {
-		var s = [];
-
+		var s = [],
+			param_traditional = jQuery.param.traditional;
+		
 		function add( key, value ){
+			// If value is a function, invoke it and return its value
+			value = jQuery.isFunction(value) ? value() : value;
 			s[ s.length ] = encodeURIComponent(key) + '=' + encodeURIComponent(value);
 		}
-
+		
 		// If an array was passed in, assume that it is an array
 		// of form elements
-		if ( jQuery.isArray(a) || a.jquery ) {
+		if ( jQuery.isArray(a) || a.jquery )
 			// Serialize the form elements
 			jQuery.each( a, function() {
 				add( this.name, this.value );
 			});
-		} else {
-			// Recursively encode parameters from object, 
-			// building a prefix path as we go down
-			function buildParams(obj, prefix)
-			{
-				if ( jQuery.isArray(obj) ) {
-					for ( var i = 0, length = obj.length; i < length; i++ ) {
-						buildParams( obj[i], prefix );
-					};
-				} else if( typeof(obj) == "object" ) {
-					for ( var j in obj ) {
-						var postfix = ((j.indexOf("[]") > 0) ? "[]" : ""); // move any brackets to the end
-						buildParams(obj[j], (prefix ? (prefix+"["+j.replace("[]", "")+"]"+postfix) : j) );
-					}
-				} else {
-					add( prefix, jQuery.isFunction(obj) ? obj() : obj );
-				}
-			}
-			buildParams(a);
-		}
+			
+		else
+			// Encode parameters from object, recursively. If
+			// jQuery.param.traditional is set, encode the "old" way
+			// (the way 1.3.2 or older did it)
+			jQuery.each( a, function buildParams( prefix, obj ) {
+				
+				if ( jQuery.isArray(obj) )
+					jQuery.each( obj, function(i,v){
+						// Due to rails' limited request param syntax, numeric array
+						// indices are not supported. To avoid serialization ambiguity
+						// issues, serialized arrays can only contain scalar values. php
+						// does not have this issue, but we should go with the lowest
+						// common denominator
+						add( prefix + ( param_traditional ? "" : "[]" ), v );
+					});
+					
+				else if ( typeof obj == "object" )
+					if ( param_traditional )
+						add( prefix, obj );
+						
+					else
+						jQuery.each( obj, function(k,v){
+							buildParams( prefix ? prefix + "[" + k + "]" : k, v );
+						});
+					
+				else
+					add( prefix, obj );
+				
+			});
 
 		// Return the resulting serialization
 		return s.join("&").replace(r20, "+");
