php - Why use CJSON encode when we have json_encode

I am building an API for a website using Yii. I know that there is a utility class called CJson and has a function called encode.

As far as I know there are additional parameters that can be customized in the native json_encode function like the JSON_NUMERIC_CHECK which is really useful. It creates

{
    "id": 17
}

instead of Yii's CJSON encode which makes the '17' a string.

{
    "id": "17"
}

So my question is whether there is any reason I should use CJSON encode instead of the built in PHP function json_encode ?