Description:
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Can you please:
1. add an option to send unquoted keys smth like JSON_UNQUTED_KEYS.
2. make json_decode to be able to decode json with unquoted keys. Now json_decode returns null if given a specification-correct json with no key quotes.

Json specification allows keys to be unquoted. If json keys are unquoted this saves up to 5-25% of json file size. 5-25% is a lot. 

This is a bit similar to JSON_UNESCAPED_UNICODE. If you send non-latin json safe chars with your utf8 webserver this is a big overhead in json file size. 5-25% too.

Test script:
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json_encode(["a"=>"b"],JSON_UNQUOTED_KEYS|JSON_UNESCAPED_UNICODE);

Expected result:
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{a:"b"}

Actual result:
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{"a":"b"}