如何使用文件的内容而不是`curl_file_create`函数的文件名？

Question

The first parameter of the curl_file_create function is the filename. Is there a way to directly use the content of the file?
I do not want to write content in a temporary file and use that filename in the function.

More expand:
I get an image from URL with $image = file_get_contents('http://example.com/image.jpg'); function, and so I have a $image variable with binary image content for now, After get it I need to post this image as part of form to another URL instantly without use temporary file on disk.

Answer 1

to anyone thinking about doing this: it's almost certainly not worth the hassle. it's possible, sure, but you'd almost certainly want to use the tmpfile() trick instead, for example if you have a variable called $file_content that you want to upload as a file, but you don't have a file, do

<?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.

.. and with a bit of luck, as long as the upload is quick and we don't call fflush($tmph);, the file may never touch the actual disk anyway, it will just be created in the IO cache, scheduled to be written to disk later, then deleted (from the io cache) - also this code is protected by PHP's garbage collector, if there's an uncaught exception/error in the code which stops execution, PHP's garbage collector will delete the file for us..

However, here's how to actually upload a file in the Multipart/form-data -format without having nor creating an on-disk file, by creating the Multipart/form-data -request with userland PHP code:

usage example:

<?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);
// shitty_multipart-way: 
$post_data = array();
$tmp = new shitty_multipart_variable();
$tmp->post_name = 'sample_variable';
$tmp->content = 'anything';
$post_data[] = $tmp;
$tmp = new shitty_multipart_file();
$tmp->post_name = 'file';
$tmp->post_file_name = "file.ext";
$tmp->content = 'contents of file.ext';
$post_data[] = $tmp;
$content_type_header="";
$post_body=shitty_multipart_form_data_generator($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);

implementation:

class shitty_multipart_file
{
    public $post_name = "";
    public $file_name = "";
    public $content_type = "application/octet-stream";
    public $content = "";
    public $additional_headers = [];
}
class shitty_multipart_variable
{
    public $post_name = "";
    public $content = "";
    public $additional_headers = [];
}
function shitty_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, 'shitty_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, 'shitty_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 shitty_multipart_variable NOR an instance of shitty_multipart_file!");
        }
    }
    $body .= $boundary . "--\r\n";
    return $body;
}