Use a 2-step update process to install requirements

The mongodb-adapter has to be installed while ignoring platform reqs,
then it can be ignored again, see https://github.com/alcaeus/mongo-php-adapter

.travis/before_install_test.sh

@@ -1,23 +1,18 @@
 #!/usr/bin/env sh
 set -ev
 
+PHP_INI_DIR="$HOME/.phpenv/versions/$(phpenv version-name)/etc/conf.d/"
+TRAVIS_INI_FILE="$PHP_INI_DIR/travis.ini"
+if [ "$DOCTRINE_ODM" != "" ]
+then
+    composer require "doctrine/mongodb-odm:$DOCTRINE_ODM" --no-update
+    echo "extension=mongodb.so" >> "$TRAVIS_INI_FILE"
+fi
+
 if [ "${TRAVIS_PHP_VERSION}" != "hhvm" ]; then
-    PHP_INI_DIR="$HOME/.phpenv/versions/$(phpenv version-name)/etc/conf.d/"
-    TRAVIS_INI_FILE="$PHP_INI_DIR/travis.ini"
     echo "memory_limit=3072M" >> "$TRAVIS_INI_FILE"
-
-
-        if [ "$TRAVIS_PHP_VERSION" '<' '7.0' ]; then
-        echo "extension=mongo.so" >> "$TRAVIS_INI_FILE"
-    else
-        echo "extension=mongodb.so" >> "$TRAVIS_INI_FILE"
-
-        # Backwards compatibility with old mongo extension
-        composer require "alcaeus/mongo-php-adapter" --no-update
-    fi
-    fi
+fi
 
 sed --in-place "s/\"dev-master\":/\"dev-${TRAVIS_COMMIT}\":/" composer.json
 
 if [ "$SYMFONY" != "" ]; then composer require "symfony/symfony:$SYMFONY" --no-update; fi;
-if [ "$DOCTRINE_ODM" != "" ]; then composer require "doctrine/mongodb-odm:$DOCTRINE_ODM" --no-update; fi;

.travis/install_test.sh

@@ -4,12 +4,7 @@ set -ev
 mkdir --parents "${HOME}/bin"
 
 # PHPUnit install
-if [ ${TRAVIS_PHP_VERSION} '<' '5.6' ]; then
-    PHPUNIT_PHAR=phpunit-4.8.phar
-else
-    PHPUNIT_PHAR=phpunit-5.7.phar
-fi
-wget "https://phar.phpunit.de/${PHPUNIT_PHAR}" --output-document="${HOME}/bin/phpunit"
+wget "https://phar.phpunit.de/phpunit-5.7.phar" --output-document="${HOME}/bin/phpunit"
 chmod u+x "${HOME}/bin/phpunit"
 
 # Coveralls client install
@@ -23,4 +18,9 @@ if [ "${COMPOSER_FLAGS}" = '--prefer-lowest' ]; then
     composer update --prefer-dist --no-interaction --prefer-stable --quiet --ignore-platform-reqs
 fi
 
+if [ "$DOCTRINE_ODM" != "" ]
+then
+    # Backwards compatibility with old mongo extension
+    composer require "alcaeus/mongo-php-adapter" --ignore-platform-reqs
+fi
 composer update --prefer-dist --no-interaction --prefer-stable ${COMPOSER_FLAGS}