Description:
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It would be nice to add a json safety feature to prevent XSS attacks. 
There is already a popular implementation of the client end of this, 
which is described here: http://www.prototypejs.org/learn/json

My request is to add an optional param to json_encode so that it 
produces output which is compatible with that of prototype. Any other 
JS library will still be compatible wih that approach. In short, wrap 
json_encode output in comments like so:

$json_output = "/*-secure-\n".json_encode($myvar)."*/";

A new implementation might achieve this as:

$json_output = json_encode($myvar, true);

I'm suggesting doing this in the ext rather than in user code as it's 
something that will likely be used a lot, and the syntax is easy to 
get wrong.