Install SDK and Virgil Crypto LibraryWith Virgil SDK you can easily communicate with Virgil Services and manage a user's Public Keys.In order to perform cryptographic operations, SDK uses a Virgil Crypto library. The Virgil SDK is provided as a package named virgil/sdk. The package is distributed via composer package management system.You need to install php virgil crypto extension ext-virgil_crypto_php as one of dependency otherwise you will get the requested PHP extension virgil_crypto_php is missing from your system error during composer install.In general to install virgil crypto extension follow next steps:Download proper extension package for your platform from cdn like virgil-crypto-2.0.4-php-5.6-linux-x86_64.tgz.Type following command to unpack extension in terminal:$ tar -xvzf virgil-crypto-2.0.4-php-5.6-linux-x86_64.tgzPlace unpacked virgil_crypto_php.so under php extension path.Add virgil extension to your php.ini configuration file like extension = virgil_crypto_php.so.$ echo "extension=virgil_crypto_php.so" >> \ `php --ini | grep "Loaded Configuration" | sed -e "s|.*:\s*||"`All necessary information about where php.ini or extension_dir are you can get from php_info() in case run php on server or call php -i | grep php.ini or php -i | grep extension_dir from CLI.Prerequisites:PHP 5.6.*Composervirgil_crypto_php.soInstalling the package:$ composer require virgil/sdk