WordPress "Expect" header fix

expect-header-fix.php

<?php

/**
 * By default, cURL sends the "Expect" header all the time which severely impacts
 * performance. Instead, we'll send it if the body is larger than 1 mb like
 * Guzzle does.
 */
function add_expect_header(array $arguments)
{
    $arguments['headers']['expect'] = '';
    
    if (is_array($arguments['body'])) {
        $bytesize = 0;
        $iterator = new RecursiveIteratorIterator(new RecursiveArrayIterator($arguments['body']));

        foreach ($iterator as $datum) {
            $bytesize += strlen((string) $datum);

            if ($bytesize >= 1048576) {
                $arguments['headers']['expect'] = '100-Continue';
                break;
            }
        }
    } elseif (!empty($arguments['body']) && strlen((string) $arguments['body']) > 1048576) {
        $arguments['headers']['expect'] = '100-Continue';
    }

    return $arguments;
}
add_filter('http_request_args', 'add_expect_header');

@nawawi you're right. I just put assumed it was always a string. I think something like this would work:

function add_expect_header(array $arguments)
{
    $body = $arguments['body']

    if (is_array($body)) {
        $body = implode('', $body);
    }

    $arguments['headers']['expect'] = !empty($body) && strlen($body) > 1048576 ? '100-Continue' : '';
    
    return $arguments;
}

@carlalexander thanks!

Hi Carl,
sorry for a noob question but can you describe what kind of website would benefit from your code? Where would I need to look to measure of the impact when I implement it? Or what kind of plugins or functions creates the problem your code solve?
Thank you very much!

@WpSpeedDoctor Any code that uses the HTTP API to make requests can benefit from this change. You could measure the impact with a plugin like Query Monitor that tracks how long HTTP requests take. It's not guaranteed to make a difference, but the impact is either "no change from before" or a "significant reduction in time".

If you want to read more about it, there's a thread that discusses the issue on the cURL mailing list.

Will it be enough to put this into a Child theme’s function.php or does this need to go into the root folder? Sorry if this question is too noob-ish, @carlalexander. Thanks!

@carlalexander came here to report the body being an array issue, you might want to take your follow up code and make an official revision to this gist.

Also the first line in that updated version is missing a colon ;

And I think the time savings on the wp-admin/update-core.php page alone could be worth the addition.

Hi, this should fix the body being array issue:

function add_expect_header(array $arguments)
{
    $body = $arguments['body'];

    if (is_array($body) || is_object($body)) {
        $body = json_encode($body);
    }

    $arguments['headers']['expect'] = !empty($body) && strlen($body) > 1048576 ? '100-Continue' : '';
    
    return $arguments;
}

@indysigner sorry I just saw this now. I missed your notification. functions.php should be fine.

@danieliser @nawawi Yeah, there were a few issues with the code when developing a patch for core. I've updated the gist with the core patch.

FYI for anyone tracking this issue. I worked on core on a fix here. I think it'll be live once WordPress 5.8 lands. It's not in as of 5.7.2.

@carlalexander noted with thanks.

It works great, but i still get "Array to string conversion", on this line:

$body = $arguments['body'];

    if ( is_array( $body ) )
	{
        $body = implode('', $body);  // not always, but sometimes i get "Array to string conversion" notice
    }

I'm not yet ready for WP 5.8, since big changes in widgets and my woocommerce plugins, etc

@Lolosan do you still get it with the updated code?

@Lolosan do you still get it with the updated code?

Thank you for the updated code, I'm testing in a woocommerce site with heavy use of APIs and everything seems great

This fix already comes with WP5.8, right? No need to use it after?

@Lolosan That's correct 😄