PHP cURL调用langSearch API报400错误的排查及解决代码

问题描述 #

调用langSearch的v1/web-search接口时，出现400 Bad Request错误，var_dump($response)返回null。官方提供的bash cURL示例如下：

curl --location 'https://api.langsearch.com/v1/web-search' \
--header 'Authorization: Bearer YOUR-API-KEY' \
--header 'Content-Type: application/json' \
--data '{
    "query": "tell me the highlights from Apple 2024 ESG report",
    "freshness": "noLimit",
    "summary": true,
    "count": 10
}'

我编写的PHP代码如下：

function web_search_with_langsearch($query) {
    $LANGSEARCH_KEY = "sk-nnnnnnnnnnnnnnnnnnnnn";
    $ENDPOINT = "https://api.langsearch.com/v1/web-search";
    $params = [
        "query" => $query,
        "freshness" => "noLimit",
        "summary" => true,
        "count" => 10
    ];
    $headers = [
        "Authorisation: Bearer " . $LANGSEARCH_KEY,
        "Content Type: application/json"
    ];
    $payload = json_encode($params);
    $curl = curl_init();
    curl_setopt($curl, CURLOPT_URL, $ENDPOINT);
    curl_setopt($curl, CURLOPT_RETURNTRANSFER, true);
    curl_setopt($curl, CURLOPT_POST, true);
    curl_setopt($curl, CURLOPT_VERBOSE, true);
    curl_setopt($curl, CURLOPT_HTTPHEADER, $headers);
    curl_setopt($curl, CURLOPT_POSTFIELDS, $params);

    $streamVerboseHandle = fopen('php://temp', 'w+');
    curl_setopt($curl, CURLOPT_STDERR, $streamVerboseHandle);


    $response = curl_exec($curl);
    curl_close($curl);

    rewind($streamVerboseHandle);
    $verboseLog = stream_get_contents($streamVerboseHandle);

    echo "cUrl verbose information:\n", 
         "<pre>", htmlspecialchars($verboseLog), "</pre>\n";

    $jsonContent = json_decode(strip_tags($response), true);
    var_dump($jsonContent);
    return $jsonContent;
}

verbose日志显示400错误：

PHP Messages: cUrl verbose information:
* About to connect() to api.langsearch.com port 443 (#0)
*   Trying 47.236.117.232...
* Connected to api.langsearch.com (47.236.117.232) port 443 (#0)
* Initializing NSS with certpath: sql:/etc/pki/nssdb
*   CAfile: /etc/pki/tls/certs/ca-bundle.crt
  CApath: none
* SSL connection using TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256
* Server certificate:
*   subject: CN=api.langsearch.com
*   start date: Aug 04 00:00:00 2025 GMT
*   expire date: Aug 03 23:59:59 2026 GMT
*   common name: api.langsearch.com
*   issuer: CN=Encryption Everywhere DV TLS CA - G2,OU=www.digicert.com,O=DigiCert Inc,C=US
> POST /v1/web-search HTTP/1.1
Host: api.langsearch.com
Accept: */*
Authorisation: Bearer sk-nnnnnnnnnnnnnnnnnnn
Content Type: application/json
Content-Length: 447
Expect: 100-continue
Content-Type: multipart/form-data; boundary=----------------------------3770c64b7bb1

< HTTP/1.1 100 Continue
< HTTP/1.1 400 
< Date: Sat, 30 May 2026 17:04:42 GMT
< Content-Type: text/html;charset=utf-8
< Content-Length: 435
< Connection: keep-alive
< Content-Language: en
* HTTP error before end of send, stop sending
<
* Closing connection 0

错误原因分析 #

从日志和代码中可以定位几个关键问题：

• 请求头拼写错误：Authorisation应为Authorization，Content Type应为Content-Type（字段名中间是连字符，不是空格）
• POST数据格式错误：传递了数组$params而非JSON字符串$payload，导致cURL自动将请求内容类型设为multipart/form-data，不符合API要求的application/json
• 缺少错误检查：未捕获cURL执行过程中的错误，无法及时排查问题

修正后的可运行代码 #

function web_search_with_langsearch($query) {
    $LANGSEARCH_KEY = "sk-nnnnnnnnnnnnnnnnnnnnnn";
    $ENDPOINT = "https://api.langsearch.com/v1/web-search";
    $params = [
        "query" => $query,
        "freshness" => "noLimit",
        "summary" => true,
        "count" => 2
    ];
    $headers = [
        "Authorization: Bearer " . $LANGSEARCH_KEY,
        "Content-Type: application/json"
    ];
    $payload = json_encode($params);
    $curl = curl_init();
    curl_setopt($curl, CURLOPT_URL, $ENDPOINT);
    curl_setopt($curl, CURLOPT_RETURNTRANSFER, true);
    curl_setopt($curl, CURLOPT_POST, true);
    curl_setopt($curl, CURLOPT_VERBOSE, true);
    curl_setopt($curl, CURLOPT_HTTPHEADER, $headers);
    curl_setopt($curl, CURLOPT_POSTFIELDS, $payload);

    $streamVerboseHandle = fopen('php://temp', 'w+');
    curl_setopt($curl, CURLOPT_STDERR, $streamVerboseHandle);
    
    // 添加cURL执行错误检查
    if(curl_exec($curl) === false){
        echo 'Curl error: ' . curl_error($curl);
    }

    $response = curl_exec($curl);
    curl_close($curl);

    rewind($streamVerboseHandle);
    $verboseLog = stream_get_contents($streamVerboseHandle);

    echo "cUrl verbose information:\n", "<pre>", htmlspecialchars($verboseLog), "</pre>\n";

    var_dump($response);
    $jsonContent = json_decode(strip_tags($response), true);
    var_dump($jsonContent);
    return $jsonContent;
}

关键修正点 #

1. 修复了请求头的拼写和格式错误，确保符合API的要求
2. 将POST数据改为传递JSON编码后的字符串，保证请求体为JSON格式
3. 添加了cURL执行错误检查，便于快速定位问题
4. 调整count参数为2（可选修改，不影响核心功能）

内容的提问来源于stack exchange，提问作者TJS101