How do I enable cURL in PHP?
Check the php version, If you installed php 7.0 version
sudo apt-get install php7.0-curl
sudo service apache2 restart
If you installed php 5.6 version
sudo apt-get install php5-curl
sudo service apache2 restart
If none of the above solves your problem and have installed with php-x86 (Windows 32 bit), then problem may be of openssl - for more info : How to fix libeay32.dll was not found error