[IMPORTANT] Platform check is causing to broke websites with unfair way

[jakubboucek]

Composer from version 2.3.0 can be application runtime afflicted by unpredicted Composer's platform check.

composer/src/Composer/Autoload/AutoloadGenerator.php

Lines 888 to 894 in 5770fb0

	// autoload.php @generated by Composer
	if (PHP_VERSION_ID < 50600) {
	echo 'Composer 2.3.0 dropped support for autoloading on PHP <5.6 and you are running '.PHP_VERSION.', please upgrade PHP or use Composer 2.2 LTS via "composer self-update --2.2". Aborting.'.PHP_EOL;
	exit(1);
	}

It is understandable and justified, but completely poorly implemented. This is same problem as I reported formerly at #9411 and fixed at #9410, #9414 and #9418.

Problems:

• Web application is stopped and replaced with the some error message, but presented with HTTP 200 OK status code. This can ruin SEO reputation!
• In CLI is error message presented simply to standard output instead of error output.
• Developer is not notified because is not any standard error mechanism triggered.

It's now shutdowns websites across the world.
Trust me its't very serious problem, try to search -echo "Composer 2.3.0 dropped support for autoloading on PHP <5.6 and you are running" for proof.

Please fix that with same way as another platform check (see above to previous PR references):

composer/src/Composer/Autoload/AutoloadGenerator.php

Lines 849 to 868 in 5770fb0

	// platform_check.php @generated by Composer
	\$issues = array();
	{$requiredPhp}{$requiredExtensions}
	if (\$issues) {
	if (!headers_sent()) {
	header('HTTP/1.1 500 Internal Server Error');
	}
	if (!ini_get('display_errors')) {
	if (PHP_SAPI === 'cli' || PHP_SAPI === 'phpdbg') {
	fwrite(STDERR, 'Composer detected issues in your platform:' . PHP_EOL.PHP_EOL . implode(PHP_EOL, \$issues) . PHP_EOL.PHP_EOL);
	} elseif (!headers_sent()) {
	echo 'Composer detected issues in your platform:' . PHP_EOL.PHP_EOL . str_replace('You are running '.PHP_VERSION.'.', '', implode(PHP_EOL, \$issues)) . PHP_EOL.PHP_EOL;
	}
	}
	trigger_error(
	'Composer detected issues in your platform: ' . implode(' ', \$issues),
	E_USER_ERROR
	);
	}

Please be always very very careful when you adding any check/error message which is fired at autoload runtime! Composer have enormous power, they should also have enormous responsibility.

[derrabus]

If you need to stay compatible with ancient versions of PHP (no judgement here), I'd strongly recommend to use Composer 2.2 instead. It's an LTS version that is still maintained to accomodate projects like yours.

The world has moved on and this version check that troubles you right now indicates that the authors of Composer cannot guarantee anymore that the generated autoloader code will be compatible with the PHP version your project is running on.

[stof]

@derrabus it would still be a good idea to build it on the same reporting way than the platform checks, which were designed to break in a good way (reporting a 500 error and not a 200 error)

[jakubboucek]

@derrabus Dropping support of legacy is OK. This issue is only HOW is dropping implemented.

[Seldaek]

Sorry about that. Hopefully resolved by c447c12 - tho it'll still kill websites, just in a nicer way. I guess this is due to shared hosts upgrading things automatically without checking compatibility at all?

[jakubboucek]

tho it'll still kill websites, just in a nicer way.

Yes, it's what I ask. The fair kill. Thanks.

Upgrades are maked automatically by lot of (semi-)automated app hosting, like a clouds and similar one. The problem lies in the detail, here can be not any change in runtime (PHP version, server, atc.), neither app itself, but can be upgraded build tool only (Composer) which is not presented to production. Only modicum od developer expects trap here wen nothich in APP nor Runtime changed.