PHP string parameter best practice - php

Question

I have a PHP function that internally builds an object graph using among other things one string parameter, then uses json_encode() to create a JSON string and then post the JSON string to a remote web service.
Like this:
function send($text)
{
$payload = array(
'text' => $text
// Set additional properties here ...
);
$payload_json = json_encode($payload);
// Post $payload_json to remote service with Curl ...
}
From the manual of json_encode (http://php.net/manual/en/function.json-encode.php)
All string data must be UTF-8 encoded.
I see a couple of options:
Attempt to validate that $text is in fact UTF-8 and throw an exception if it is not
Attempt to detect the encoding in $text and convert it to UTF-8 if necessary
Return false when $text is not UTF-8
Communicate with my API users in documentation that $text must be UTF-8
Check for error with json_last_error() and throw an exception if an error was encountered
What is the best practice?

Answer 1

You should always communicate to the users of the API what you're expecting.
If you expect UTF-8 encoded text, say so in your documentation.
Once it's in there, you should return a descriptive error such as "Invalid Encoding, for more information read the documentation: link" where link goes to the relevant page for the call that failed
This way, you're not responsible anymore, and the developers that use your API will know what is going wrong, and you don't have to worry about it in your API.
You're the developer, it's your API, and your API has it's own rules, if people want to use it, they need to follow the rules you set.