这是可能的，当然，但你几乎肯定要使用 tmpfile（）技巧，例如，如果你有一个名为$file_content的变量，你想上传一个文件，但你没有一个文件，做

<?php
$file_content = "the content of the *file* i want to upload, which does not exist on disk";
$file_name = "example.bin";
$tmph = tmpfile(); // will create a file in the appropriate temp folder when an unique filename
fwrite($tmph, $file_content);
$tmpf = stream_get_meta_data($tmph)['uri'];
$ch = curl_init('http://target_url/');
curl_setopt_array($ch, array(
    CURLOPT_POST => 1,
    CURLOPT_POSTFIELDS => array(
        'file' => new CURLFile($tmpf, 'application/octet-stream', $file_name)
    )
));
curl_exec($ch);
fclose($tmph); // thanks to tmpfile() magic, the file is automatically deleted when fclosed()'d
unset($tmph, $tmpf); // unset() is not needed, but this is the end of the tmpfile()-trick.

..只要上传很快，我们不调用 fflush（$tmph）;，文件可能永远不会接触实际的磁盘，它只是在 IO 缓存中创建，计划稍后写入磁盘，然后删除（从 io 缓存）-这个代码也受到 PHP 的垃圾收集器的保护，如果代码中有一个未捕获的异常 / 错误停止执行，PHP 的垃圾收集器文件将删除

然而，这里是如何实际上传的Multipart/form-data格式的文件，而无需也不创建一个磁盘上的文件，通过创建Multipart/form-data-请求与 userland PHP 代码：

用法示例：

<?php
// normal php-way: 
$ch = curl_init();
curl_setopt_array($ch, array(
    CURLOPT_URL=>'https://example.com/',
    CURLOPT_POST => 1,
    CURLOPT_POSTFIELDS => array(
        'sample_variable' => 'anything',
        'file' => new CURLFile("path/to/file.txt")
    )
));
curl_exec($ch);
curl_close($ch);
// ty_multipart-way: 
$post_data = array();
$tmp = new ty_multipart_variable();
$tmp->post_name = 'sample_variable';
$tmp->content = 'anything';
$post_data[] = $tmp;
$tmp = new ty_multipart_file();
$tmp->post_name = 'file';
$tmp->post_file_name = "file.ext";
$tmp->content = 'contents of file.ext';
$post_data[] = $tmp;
$content_type_header="";
$post_body=ty_multipart_form_data_generator($post_data,$content_type_header);
$ch = curl_init();
curl_setopt_array($ch, array(
    CURLOPT_URL=>'https://example.com/',
    CURLOPT_POST => 1,
    CURLOPT_POSTFIELDS => $post_body,
    CURLOPT_HTTPHEADER=>array(
        $content_type_header
    )
));
curl_exec($ch);
curl_close($ch);

实现：

cl ty_multipart_file
{
    public $post_name = "";
    public $file_name = "";
    public $content_type = "application/octet-stream";
    public $content = "";
    public $additional_headers = [];
}
cl ty_multipart_variable
{
    public $post_name = "";
    public $content = "";
    public $additional_headers = [];
}
function ty_multipart_form_data_generator(array $postfields, string &$out_content_type_header): string
{
    // Content-Type: multipart/form-data; boundary=------------------------7b5b9abe8c56fd67
    // same boundary format as used by curl
    $boundary = "------------------------" . strtolower(bin2hex(random_bytes(8)));
    $out_content_type_header = 'Content-Type: multipart/form-data; boundary=' . $boundary;
    $body = "";
    foreach ($postfields as $unused => $post) {
        $body .= $boundary . "\r\n";
        if (is_a($post, 'ty_multipart_variable')) {
            $body .= "Content-Disposition: form-data; name=\"{$post->post_name}\"\r\n";
            foreach ($post->additional_headers as $header) {
                $body .= $header . "\r\n";
            }
            $body .= "\r\n";
            $body .= $post->content . "\r\n";
        } elseif (is_a($post, 'ty_multipart_file')) {
            $body .= "Content-Disposition: form-data; name=\"{$post->post_name}\"; filename=\"{$post->file_name}\"\r\n";
            $body .= "Content-Type: " . $post->content_type . "\r\n";
            foreach ($post->additional_headers as $header) {
                $body .= $header . "\r\n";
            }
            $body .= "\r\n";
            $body .= $post->content . "\r\n";
        } else {
            throw new \InvalidArgumentException("postfields key {$unused} is not an instance of ty_multipart_variable NOR an instance of ty_multipart_file!");
        }
    }
    $body .= $boundary . "--\r\n";
    return $body;
}