PHP cURL请求头与全局变量不起作用

我已经设置了一个全局变量，等于一个访问令牌，当我打印_($session_id)时，令牌是可见的。我想做的是把这个变量传给我的CURLOPT_HTTPHEADER，并在下面的函数get_field_data_id()中让它等于 "Session"。

function get_session_id() {
global $session_id;
$curl = curl_init();
$session_url = "/auth";
curl_setopt_array($curl, array(
    CURLOPT_URL => $session_url ,
    CURLOPT_RETURNTRANSFER => true,
    CURLOPT_ENCODING => "",
    CURLOPT_MAXREDIRS => 10,
    CURLOPT_TIMEOUT => 0,
    CURLOPT_FOLLOWLOCATION => true,
    CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
    CURLOPT_CUSTOMREQUEST => "GET",
    CURLOPT_HTTPHEADER => array(
        "Content-Type: application/json",
        "Accept: application/json",
        "username: USER",
        "password: PASS",
        "authorizationkey: KEY"
$response = curl_exec($curl);
curl_close($curl);
$session_id = $response;
} add_filter( 'gform_after_submission_4', 'get_session_id' );
function get_field_data_id() {
global $session_id;
$curl = curl_init();
$file_url = "URL";
curl_setopt_array($curl, array(
    CURLOPT_URL => $file_url,
    CURLOPT_RETURNTRANSFER => true,
    CURLOPT_ENCODING => "",
    CURLOPT_MAXREDIRS => 10,
    CURLOPT_TIMEOUT => 0,
    CURLOPT_FOLLOWLOCATION => true,
    CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
    CURLOPT_CUSTOMREQUEST => "GET",
    CURLOPT_HTTPHEADER => array(
        "Content-Type: application/json",
        "Accept: application/json",
        "Session: {$session_id}"
$response = curl_exec($curl);
curl_close($curl);