PHP_MD5 enviroment variable is created/dumped but empty

[mvorisek]

see https://github.com/atk4/ui/runs/1326431408#step:2:131

source image: php:7.4-alpine

[yosifkit]

That value and others, like the SHA256, are fetched from the PHP releases API (example for 7.4) and only the values that exist are put in the Dockerfile, but if it has a value, it is checked.

php/7.4/alpine3.12/cli/Dockerfile

Lines 62 to 87 in 0f0ddea

	ENV PHP_URL="https://www.php.net/distributions/php-7.4.11.tar.xz" PHP_ASC_URL="https://www.php.net/distributions/php-7.4.11.tar.xz.asc"
	ENV PHP_SHA256="5d31675a9b9c21b5bd03389418218c30b26558246870caba8eb54f5856e2d6ce" PHP_MD5=""
	RUN set -eux; \
	\
	apk add --no-cache --virtual .fetch-deps gnupg; \
	\
	mkdir -p /usr/src; \
	cd /usr/src; \
	\
	curl -fsSL -o php.tar.xz "$PHP_URL"; \
	\
	if [ -n "$PHP_SHA256" ]; then \
	echo "$PHP_SHA256 *php.tar.xz" | sha256sum -c -; \
	fi; \
	if [ -n "$PHP_MD5" ]; then \
	echo "$PHP_MD5 *php.tar.xz" | md5sum -c -; \
	fi; \
	\
	if [ -n "$PHP_ASC_URL" ]; then \
	curl -fsSL -o php.tar.xz.asc "$PHP_ASC_URL"; \
	export GNUPGHOME="$(mktemp -d)"; \
	for key in $GPG_KEYS; do \
	gpg --batch --keyserver ha.pool.sks-keyservers.net --recv-keys "$key"; \
	done; \
	gpg --batch --verify php.tar.xz.asc php.tar.xz; \

The reason for optional MD5, SHA256, and detached signature (.asc) was that some versions only had one or maybe even none (like pre-releases). Likely, we can just drop the MD5 env from the Dockerfile since no recent release has it.