Template loaded via remote storage is not displayed in the editor

urlLoad: "https://myendpoint/lib/remote_storage_load_template.php",
				    params: {},
				    contentTypeJson: true,
},

This is the PHP code from my urlLoad:

header('Content-Type: application/json');

$html = '<div class = "hero">Hello world</div>';
$css = '*{color:red;} body{width:100%;}';
$arr = array(
	'gjs-html' => $html,
	'gjs-css' => $css,
	'gjs-assets' => [],
	'gjs-styles' => [],
	'gjs-components' => []);

//echo htmlentities(json_encode($arr));
echo json_encode($arr);

This is the JSON that grapesjs loads from my endpoint:

`editor.on('storage:load', obj => console.log('Loaded ', obj));`

![image](https://user-images.githubusercontent.com/64067337/90645170-ecab1300-e235-11ea-92ef-b4314e9ba991.png)

When I make a GET request to my endpoint directly, this is what I get:
`{"gjs-html":"<div class = \"hero\">Hello world<\/div>","gjs-css":"*{color:red;} body{width:100%;}","gjs-assets":[],"gjs-styles":[],"gjs-components":[]}`

Am I missing something obvious?

Thanks for your help