是什么导致市场订单在Coinbase Exchange API上失败的PHP代码

为了自己的目的，我用PHP创建了一个功能齐全的Coinbase API系统。然而，系统中有一部分我无法正常工作：市场订单。

下面出现的代码是在面向对象系统中出现的步骤的复制。我认为在这个论坛中，线性代码比挖掘继承层更容易解决问题。

Coinbase API返回错误消息，如代码底部的注释文本所示。API的"市场"订单不需要"价格"参数，此处介绍：Coinbase Exchange API文档。当我通过添加请求的字段来响应错误消息时，订单最终成功，但订单被处理为"限制"订单，而不是类型所示的"市场"订单。

你能认出我犯的错误吗？

<?php
$settings = 'parse_ini_file("API.ini", true);
$apiSecret = $settings['trader_sandbox']['API Secret'];
$apiKey = $settings['trader_sandbox']['API Key'];
$apiPassPhrase = $settings['trader_sandbox']['Passphrase'];
$urlBase = "https://api-public.sandbox.exchange.coinbase.com";
//get timestamp
$date = new 'DateTime("now", new 'DateTimeZone("America/Los_Angeles"));
$timestamp = $date->getTimestamp();
//API url
$relUrl = "/orders";
//set the method type GET|POST|DELETE|PUT
$method = "POST";
$params = [
    "type" => "market",
    "side" => "sell",
    "product_id" => "BTC-USD",
    "stp" => "dc",
    "size" => "0.10000000"
];
//copied from coinbase's documentation added apiSecret
function signature($request_path = '', $body = '', $timestamp = false, $method = 'GET', $apiSecret=null) {
    /**
     * Modified $body assignment to exclude empty bodies
     * @author Jared Clemence <jaredclemence@alum.drexel.edu>
     * @ref https://community.coinbase.com/t/get-fills-invalid-signature-error-php-example-included/911
     */
    $body = is_array($body) ? ( 'count($body) > 0 ? json_encode($body) : null ) : $body;
    $timestamp = $timestamp ? time() : $timestamp;
    $what = $timestamp . $method . $request_path . $body;
    return base64_encode(hash_hmac("sha256", $what, base64_decode($apiSecret), true));
}
$url = $urlBase . $relUrl;
$ch = curl_init($url);
$output = 'json_encode($params);
$signature = 'signature($relUrl, $output, $timestamp, $method, $apiSecret);
$headers = [
    "User-Agent" => "Traderbot/v1.0",
    "CB-ACCESS-KEY" => $apiKey,
    "CB-ACCESS-SIGN" => $signature,
    "CB-ACCESS-TIMESTAMP" => $timestamp,
    "CB-ACCESS-PASSPHRASE" => $apiPassPhrase,
    "Content-Type" => "application/json"
];
'curl_setopt($ch, CURLOPT_POST, true);
'curl_setopt($ch, CURLOPT_POSTFIELDS, $output);
foreach ($headers as $key => &$header) {
    //this I found is necessary. Before I added this, the headers lacked the field data and only had the content values
    $header = "{$key}:$header";
}
'curl_setopt($ch, CURLOPT_HTTPHEADER, $headers);
'curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
$result = curl_exec($ch);
'curl_close($ch);
try {
    $newResult = 'json_decode($result);
    $result = $newResult;
} catch (Exception $ex) {
}
var_dump( $result );
/**
 * 
 * Output:
class stdClass#2 (1) {
  public $message =>
  string(13) "Invalid price"
}
 */