api.php

<?php

$rpcUser = "test";
$rpcPass = "test";
$rpcUrl  = "http://localhost:19918/";

function rpc($method, $params = []) {
    global $rpcUser, $rpcPass, $rpcUrl;

    $payload = json_encode([
        "jsonrpc" => "1.0",
        "id" => "web",
        "method" => $method,
        "params" => $params
    ]);

    $ch = curl_init($rpcUrl);
    curl_setopt_array($ch, [
        CURLOPT_RETURNTRANSFER => true,
        CURLOPT_HTTPAUTH => CURLAUTH_BASIC,
        CURLOPT_USERPWD => "$rpcUser:$rpcPass",
        CURLOPT_POST => true,
        CURLOPT_POSTFIELDS => $payload,
        CURLOPT_HTTPHEADER => ["Content-Type: application/json"]
    ]);

    $res = curl_exec($ch);
    if ($res === false) {
        http_response_code(500);
        exit("RPC error: " . curl_error($ch));
    }

    $data = json_decode($res, true);
    if ($data["error"]) {
        http_response_code(500);
        exit($data["error"]["message"]);
    }

    return $data["result"];
}

$action = $_GET["action"] ?? "";

if ($action === "utxos") {
    $address = $_GET["address"];
    echo json_encode(
        rpc("listunspent", [1, 9999999, [$address]])
    );
}

if ($action === "broadcast") {
    $raw = json_decode(file_get_contents("php://input"), true)["rawtx"];
    echo json_encode([
        "txid" => rpc("sendrawtransaction", [$raw])
    ]);
}

if ($action === "balance") {
    $address = $_GET["address"];
    rpc("importaddress", [$address, "", false]);
    $utxos = rpc("listunspent", [0, 9999999, [$address], true]);
    $total = 0;
    foreach ($utxos as $utxo) {
        $total += $utxo["amount"];
    }
    $balance = $total;
    echo json_encode([
        "balance" => $balance
    ]);
}