如何使用PHP实现微信小程序的文件分享功能？

<?php
$appid = 'your_appid';
$secret = 'your_secret';
$api = "https://api.weixin.qq.com/cgi-bin/token?grant_type=client_credential&appid={$appid}&secret={$secret}";

$response = file_get_contents($api);
$arr = JSON_decode($response, true);

$access_token = $arr['access_token'];
?>

<?php
$file_path = 'your_file_path';
if (move_uploaded_file($_FILES['file']['tmp_name'], $file_path)) {
    echo "文件上传成功";
} else {
    echo "文件上传失败";
}
?>

<?php
$file_name = 'your_file_name';
$share_url = 'your_share_url';

$share_url = $share_url . '?' . http_build_query([
    'file' => $file_name
]);
echo $share_url;
?>

<?php
$file_name = $_GET['file'];
$file_path = 'your_file_path/' . $file_name;

header('Content-Type: application/octet-stream');
header('Content-Disposition: attachment; filename="' . $file_name . '"');

readfile($file_path);
?>