What is "traditional style of param serialization' in JQuery

Do you know what is "traditional style of param serialization" for jQuery.ajax() as mentioned in http://api.jquery.com/jQuery.ajax/ ?

Can you give some introduction?

Thanks

Have a look at the documentation of jQuery.param():

As of jQuery 1.4, the $.param() method serializes deep objects recursively to accommodate modern scripting languages and frameworks such as PHP and Ruby on Rails. You can disable this functionality globally by setting jQuery.ajaxSettings.traditional = true;.

Given

var p = {foo: [1,2,3], bar: 42};

setting traditional to true generates

foo=1&foo=2&foo=3&bar=42

While e.g. Python can handle these parameters, i.e. it generates a list for foo, PHP will only consider the last foo parameter.

But now by default, the result of the serialization is (actually it is URI encoded)

foo[]=1&foo[]=2&foo[]=3&bar=42

which can be better handled, as mentioned, by PHP and RoR.

Or maybe even more interesting is this. Given:

var p = {foo: {1: [3,4], 2:2,3:3}, bar: 42};

traditional produces:

foo=[object Object]&bar=42

which is clearly not useful in comparison with the "new" way:

foo[1][]=3&foo[1][]=4&foo[2]=2&foo[3]=3&bar=42