curl_getinfo($ch, CURLINFO_CONTENT_TYPE) returns false when Content-Type header is not set

[ondrejcech]

Description

The following code:

<?php
$ch = curl_init();
$url = 'https://epapucs.hu/wp-content/uploads/2024/11/F318482161_2.webp';

curl_setopt($ch, CURLOPT_URL, $url);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, $url);
curl_exec($ch);

$ct = curl_getinfo($ch, CURLINFO_CONTENT_TYPE);

var_dump($ct);

$info = curl_getinfo($ch)['content_type'];

var_dump($info);

curl_close($ch);

Resulted in this output:

bool(false)
NULL

I'd expect these two values to be the same. It's hard to handle errors when a false value is returned when there's no error.

These are the first elements of curl_getinfo associative_array:

array(41) {
  ["url"]=>
  string(63) "https://epapucs.hu/wp-content/uploads/2024/11/F318482161_2.webp"
  ["content_type"]=>
  NULL
  ["http_code"]=>
  int(200)

PHP Version

PHP 8.4.1

Operating System

macOS 15.1

[cmb69]

php-src/ext/curl/interface.c

Lines 2501 to 2502 in ba8e3e1

	ZVAL_NULL(&retnull);
	CAAZ("content_type", &retnull);

vs.

php-src/ext/curl/interface.c

Line 2670 in ba8e3e1

RETURN_FALSE;

The fix is trivial, but given the long standing behavior, it might be best to only fix for master (and maybe for PHP 8.4).

[MarcusXavierr]

@cmb69
So, the issue here is curl_getinfo($ch, CURLINFO_CONTENT_TYPE) returning false as a fallback for no info. Could just changing line 2670 break some programs that already expect curl_getinfo($ch, X) to return false? This seems to be the default for all other options.

Would setting the content_type to false on line 2502 be the best approach? I think it seems semantically weird, but it seems to be the option with less change on the actual code behavior

[cmb69]

See #16997 (comment).