I’m trying to create show transaction from Coinbase Api in php but I don’t get any response from Coinbase Api

I’m trying to create show transaction from Coinbase Api in php but I don’t get any response from the Coinbase api

<?php

function sendTransaction($private_key, $api_key , $transaction_id , $account_id){
    $json = new stdClass();
    $json->method = "GET";
    $json->path = "/v2/accounts/".$account_id."/transactions/".$transaction_id."";
    $json->secretapikey = $private_key;
    $json->apikey = $api_key;

    $body = new stdClass();
    $body->type = "read";
    $body->transaction_id = $transaction_id;

    $result = json_encode($json);
    $body = json_encode($body);
    $time= time();
    $sign = $time.$json->method.$json->path.$body;
    $hmac = hash_hmac("SHA256", $sign, $json->secretapikey);

    $header = array(
        "CB-ACCESS-KEY:".$api_key,
        "CB-ACCESS-SIGN:".$hmac,
        "CB-ACCESS-TIMESTAMP:".time(),
        "CB-VERSION:2019-11-15",
        "Content-Type:application/json"
    );

    $ch = curl_init($URL);
    curl_setopt($ch, CURLOPT_POSTFIELDS, $body);
    curl_setopt($ch, CURLOPT_HTTPHEADER,$header);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
    $result = curl_exec($ch);
    curl_close($ch);

    return $result;
};

//Creating URL For Sending Request
$account_id = 'a2ae96db-c4f6-5364-b4d3-dd142af658c9'; //Coinbase Account ID
$private_key = 'QyxtlM3nKpI9E6U6aZXpIN**'; //Coinbase Private Key
$api_key = '4d13sW2jCJ**'; //Coinbase API KEY
$transaction_id = '1313a82c-10fc-532e-bc75-90801f482d74'; //Transaction id

$url = "https://api.coinbase.com/v2/accounts/".$account_id."/transactions/".$transaction_id."";

$tranx_id = sendTransaction(
    $private_key,
    $api_key,
    $transaction_id,
    $account_id
);

print_r($tranx_id);
?>

Here is the documentation url
https://docs.cloud.coinbase.com/sign-in-with-coinbase/docs/api-transactions

documentation image