How to fix curl_multi_setopt(): CURLPIPE_HTTP1 is no longer supported in composer

When you for example upgrade to PHP 7.4 and you try to install your composer dependencies, and you get this error:

Loading plugin Symfony\Flex\Flex

                                                              
  [ErrorException]                                            
  curl_multi_setopt(): CURLPIPE_HTTP1 is no longer supported

then the error is not actually coming from composer, but from symfony flex. This is the issue on github.

They fixed it but to apply the fix is not that easy, because you will be locked with your broken symfony flex dependency.

Fix it with:

rm -r vendor/symfony/flex
composer update -v symfony/flex

some reported that they had to update their global symfony flex installation first (but I had none, so it worked without)