& not encoded in JSON request

[mib]

IN JSON request & is not URL encoded and PHP can't parse this request.
In our code I create following patch to fix this problem:

Json.toUrlEncodedString = function(obj) {
	switch($type(obj)){
		case 'string':
			return '"' + encodeURIComponent(obj.replace(/(["\\])/g, '\\$1')) + '"';
		case 'array':
			return '[' + obj.map(Json.toUrlEncodedString).join(',') + ']';
		case 'object':
			var string = [];
			for (var property in obj) string.push(Json.toUrlEncodedString(property) + ':' + Json.toUrlEncodedString(obj[property]));
			return '{' + string.join(',') + '}';
		case 'number':
			if (isFinite(obj)) break;
		case false:
			return 'null';
	}
	return String(obj);
}

Json.Remote = XHR.extend({

	initialize: function(url, options){
		this.url = url;
		this.addEvent('onSuccess', this.onComplete);
		this.parent(options);
		//this.setHeader('X-Request', 'JSON');
	},

	send: function(obj){
		return this.parent(this.url, 'json=' + Json.toUrlEncodedString(obj));
	},

	onComplete: function(){
		this.fireEvent('onComplete', [Json.evaluate(this.response.text, this.options.secure)]);
	}

});