$ _GET变量在CURL POST中传递

Question

我不知道为什么下面的代码不起作用，但是当我将'page' => $page_no替换为'page' => 4时，它仍然起作用。

代码：

$page_no = $_GET['page_no'];

$base_url = 'url here';
$api_id = 'api here';
$secret = ' secret here ';

$postvars = [
    'query' => 'query here',
    'page' => $page_no,
    'fields' => ['ip', 'city','province', 'country_code', 'country'],
    'fattened' => true
];

$ch = curl_init();
curl_setopt($ch, CURLOPT_URL,$base_url);
curl_setopt($ch, CURLOPT_HTTPHEADER, array('Content-Type: application/json'));
curl_setopt($ch, CURLOPT_POST, 1); 
curl_setopt($ch, CURLOPT_POSTFIELDS, json_encode($postvars));
curl_setopt($ch, CURLOPT_RETURNTRANSFER,1);
curl_setopt($ch, CURLOPT_HTTPAUTH, CURLAUTH_BASIC);
curl_setopt($ch, CURLOPT_USERPWD, "$api_id:$secret");
curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false);
curl_setopt($ch, CURLINFO_HEADER_OUT, true);

$json = curl_exec($ch);

我使用的URL是：https://example.com/search.php?page_no=4

非常感谢您的帮助。