Send string as a file using curl and php

I know I can use this syntaxt to send a file using php, post and curl.

$post = array(
curl_setopt($ch, CURLOPT_POSTFIELDS, $post); 

How can I take a string, build a temp file and send it using the exact same syntax ?

I would prefer using tmpfile() or php://memory so I don’t have to handle file creation.

Here is Solutions:

We have many solutions to this problem, But we recommend you to use the first solution because it is tested & true solution that will 100% work for you.

Solution 1

You can create a file using tempnam in your temp directory:

$string = 'random string';

//Save string into temp file
$file = tempnam(sys_get_temp_dir(), 'POST');
file_put_contents($file, $string);

//Post file
$post = array(
curl_setopt($ch, CURLOPT_POSTFIELDS, $post);

//do your cURL work here...

//Remove the file

Solution 2

You can create a temporary file using file_put_contents, just make sure that the target directory is writable.

$path = '/path/to/myfile.txt';    
file_put_contents($myData, $path);

$post = array(
curl_setopt($ch, CURLOPT_POSTFIELDS, $post);

# Delete the file if you don't need it anymore

Solution 3


function curl_custom_postfields($ch, array $assoc = array(), array $files = array()) {
             // invalid characters for "name" and "filename"
             static $disallow = array("\0", "\"", "\r", "\n");

             // build normal parameters
             foreach ($assoc as $k => $v) {
                 $k = str_replace($disallow, "_", $k);
                 $body[] = implode("\r\n", array(
                     "Content-Disposition: form-data; name=\"{$k}\"",

             // build file parameters
             foreach ($files as $k => $v) {
                 switch (true) {
                     case false === $v = realpath(filter_var($v)):
                     case !is_file($v):
                     case !is_readable($v):
                         continue; // or return false, throw new InvalidArgumentException
                 $data = file_get_contents($v);
                 $v = call_user_func("end", explode(DIRECTORY_SEPARATOR, $v));
                 $k = str_replace($disallow, "_", $k);
                 $v = str_replace($disallow, "_", $v);
                 $body[] = implode("\r\n", array(
                     "Content-Disposition: form-data; name=\"{$k}\"; filename=\"{$v}\"",
                     "Content-Type: image/jpeg",

             // generate safe boundary
             do {
                 $boundary = "---------------------" . md5(mt_rand() . microtime());
             } while (preg_grep("/{$boundary}/", $body));

             // add boundary for each parameters
             array_walk($body, function (&$part) use ($boundary) {
                 $part = "--{$boundary}\r\n{$part}";

             // add final boundary
             $body[] = "--{$boundary}--";
             $body[] = "";

             // set options
             return @curl_setopt_array($ch, array(
                 CURLOPT_POST       => true,
                 CURLOPT_POSTFIELDS => implode("\r\n", $body),
                 CURLOPT_HTTPHEADER => array(
                     "Expect: 100-continue",
                     "Content-Type: multipart/form-data; boundary={$boundary}", // change Content-Type

$ch = curl_init();       
curl_setopt($ch, CURLOPT_URL,$url);
curl_custom_postfields($ch,$array1,$array2);//above custom function

Solution 4

Since PHP 8.1 there’s also CURLStringFile which would allow you to send it without the temporary file:

$txt = 'test content';
$file = new \CURLStringFile($txt, 'filename.txt', 'text/plain');

$ch = curl_init('');
curl_setopt($ch, CURLOPT_POST, true);
curl_setopt($ch, CURLOPT_POSTFIELDS, ['file' => $file]);

Note: Use and implement solution 1 because this method fully tested our system.
Thank you 🙂

All methods was sourced from or, is licensed under cc by-sa 2.5, cc by-sa 3.0 and cc by-sa 4.0

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