Merge pull request #10224 from deannagarcia/21.x

Cherry-pick composer fix

kokoro/linux/dockerfile/test/php_32bit/Dockerfile

@@ -47,8 +47,10 @@ RUN cd /var/local \
   && make install
 
 # Install composer
-RUN curl -sS https://getcomposer.org/installer | php
-RUN mv composer.phar /usr/local/bin/composer
+RUN php -r "copy('https://getcomposer.org/installer', 'composer-setup.php');"
+RUN php composer-setup.php
+RUN mv composer.phar /usr/bin/composer
+RUN php -r "unlink('composer-setup.php');"
 
 # Download php source code
 RUN git clone https://github.com/php/php-src

php/composer.json

@@ -9,7 +9,7 @@
     "php": ">=7.0.0"
   },
   "require-dev": {
-    "phpunit/phpunit": ">=5.0.0"
+    "phpunit/phpunit": ">=5.0.0 <8.5.27"
   },
   "autoload": {
     "psr-4": {