curl --request PUT \
  --url https://app.launchdarkly.com/api/v2/users/{projectKey}/{environmentKey}/{userKey}/flags/{featureFlagKey} \
  --header 'Authorization: <api-key>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "setting": "existing_variation_value_to_use",
  "comment": "make sure this context experiences a specific variation"
}
'

import requests

url = "https://app.launchdarkly.com/api/v2/users/{projectKey}/{environmentKey}/{userKey}/flags/{featureFlagKey}"

payload = {
    "setting": "existing_variation_value_to_use",
    "comment": "make sure this context experiences a specific variation"
}
headers = {
    "Authorization": "<api-key>",
    "Content-Type": "application/json"
}

response = requests.put(url, json=payload, headers=headers)

print(response.text)

const options = {
  method: 'PUT',
  headers: {Authorization: '<api-key>', 'Content-Type': 'application/json'},
  body: JSON.stringify({
    setting: 'existing_variation_value_to_use',
    comment: 'make sure this context experiences a specific variation'
  })
};

fetch('https://app.launchdarkly.com/api/v2/users/{projectKey}/{environmentKey}/{userKey}/flags/{featureFlagKey}', options)
  .then(res => res.json())
  .then(res => console.log(res))
  .catch(err => console.error(err));

<?php

$curl = curl_init();

curl_setopt_array($curl, [
  CURLOPT_URL => "https://app.launchdarkly.com/api/v2/users/{projectKey}/{environmentKey}/{userKey}/flags/{featureFlagKey}",
  CURLOPT_RETURNTRANSFER => true,
  CURLOPT_ENCODING => "",
  CURLOPT_MAXREDIRS => 10,
  CURLOPT_TIMEOUT => 30,
  CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
  CURLOPT_CUSTOMREQUEST => "PUT",
  CURLOPT_POSTFIELDS => json_encode([
    'setting' => 'existing_variation_value_to_use',
    'comment' => 'make sure this context experiences a specific variation'
  ]),
  CURLOPT_HTTPHEADER => [
    "Authorization: <api-key>",
    "Content-Type: application/json"
  ],
]);

$response = curl_exec($curl);
$err = curl_error($curl);

curl_close($curl);

if ($err) {
  echo "cURL Error #:" . $err;
} else {
  echo $response;
}

package main

import (
	"fmt"
	"strings"
	"net/http"
	"io"
)

func main() {

	url := "https://app.launchdarkly.com/api/v2/users/{projectKey}/{environmentKey}/{userKey}/flags/{featureFlagKey}"

	payload := strings.NewReader("{\n  \"setting\": \"existing_variation_value_to_use\",\n  \"comment\": \"make sure this context experiences a specific variation\"\n}")

	req, _ := http.NewRequest("PUT", url, payload)

	req.Header.Add("Authorization", "<api-key>")
	req.Header.Add("Content-Type", "application/json")

	res, _ := http.DefaultClient.Do(req)

	defer res.Body.Close()
	body, _ := io.ReadAll(res.Body)

	fmt.Println(string(body))

}

HttpResponse<String> response = Unirest.put("https://app.launchdarkly.com/api/v2/users/{projectKey}/{environmentKey}/{userKey}/flags/{featureFlagKey}")
  .header("Authorization", "<api-key>")
  .header("Content-Type", "application/json")
  .body("{\n  \"setting\": \"existing_variation_value_to_use\",\n  \"comment\": \"make sure this context experiences a specific variation\"\n}")
  .asString();

require 'uri'
require 'net/http'

url = URI("https://app.launchdarkly.com/api/v2/users/{projectKey}/{environmentKey}/{userKey}/flags/{featureFlagKey}")

http = Net::HTTP.new(url.host, url.port)
http.use_ssl = true

request = Net::HTTP::Put.new(url)
request["Authorization"] = '<api-key>'
request["Content-Type"] = 'application/json'
request.body = "{\n  \"setting\": \"existing_variation_value_to_use\",\n  \"comment\": \"make sure this context experiences a specific variation\"\n}"

response = http.request(request)
puts response.read_body

{
  "code": "invalid_request",
  "message": "Invalid request body"
}

{
  "code": "unauthorized",
  "message": "Invalid access token"
}

{
  "code": "forbidden",
  "message": "Forbidden. Access to the requested resource was denied."
}

{
  "code": "not_found",
  "message": "Invalid resource identifier"
}

{
  "code": "rate_limited",
  "message": "You've exceeded the API rate limit. Try again later."
}