Hi,
In the example I give is working great.
Then I tried to send all options by json to PHP, alter the theme, return also by json, change the chart options,render the chart, and the theme is not altered.

JS:

var chart = new CanvasJS.Chart("content",
{
	theme: "theme1",
	title:{
		text: "Changing Theme"
	},
	data: [
	{
		type: "column",
		dataPoints: [
		{ x: 10, y: 71 },
		{ x: 20, y: 55},
		{ x: 30, y: 50 },
		{ x: 40, y: 65 },
		{ x: 50, y: 95 },
		{ x: 60, y: 68 },
		{ x: 70, y: 28 },
		{ x: 80, y: 34 },
		{ x: 90, y: 14}
		]
	}
	]
});
chart.render();
var json=JSON.stringify(chart);

success = function(jsonObject) {
	chart.options=JSON.parse(jsonObject.chartOptions);
	chart.render();
};
jsonRequest(json,success);

PHP:

$s=json_decode ( $_REQUEST['json'] ,true);
$s['options']['theme']="theme2";
$response->chartOptions=json_encode ($s);

Br,
Daniel