Composer detected issues in your platform: Your Composer dependencies require a PHP version ">= 7.1.3". You are running 5.5.38. in code example
Example 1: Composer detected issues in your platform: Your Composer dependencies require a PHP version ">= 7.3.0".
composer install --ignore-platform-reqs
Example 2: Composer detected issues in your platform: Your Composer dependencies require a PHP version ">= 7.3.0".
#add to composer.json > config
"platform-check": false,
composer autoload-dump