Magento 2 use autoload implement Code style PSR-4 You can add any custom source lib much easier by add require autoload 1. Upload lib files to vendor dir 2. Add file autoload.php in /vendor/lib-folder/autoload.php with content define('FACEBOOK_SDK_V4_SRC_DIR', '/src/Facebook/'); require __DIR__ . '/src/Facebook/autoload.php'; 3. Save and now you can call lib from anywhere like this ---- Injection from constructor and call instance in class \Facebook\Facebook
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