It's disabled by default, but you can easily enable PHP7 in your cPanel account >> Software >> Select PHP Versions.
Along with PHP-7 you can enable modules for it. Here are some of the supported modules: gd, http, imagick, memcached, soap, xmlrpc.
PHP 7 - a revolution in the way websites and mobile applications are delivered. This is the most important change for PHP since the release of PHP 5 in 2004, bringing explosive performance improvements, drastically reduced memory consumption, and a host of brand-new language features to make your apps soar.
With PHP7 and new Zend Engine, your apps see up to 2x faster performance and 50% better memory consumption than PHP 5.6, allowing you to serve more concurrent users without adding any hardware. Designed and refactored for today’s workloads, PHP 7 is the ultimate choice for web developers today.
New Zend Engine - PHP 7 receives a brand new version of the engine coming under the code name of PHP#NG (Next Generation).
Double Speed - The most easily recognizable advantage of the new PHPNG engine is the significant performance improvement. You can see the performance benchmarks provided by the Zend Performance Team below. By using PHP 7 not only your code will be executed faster but you will also need fewer servers to serve the same amount of users.
Error Handling - Handling fatal and catchable fatal errors have never been an easy task for PHP coders. The new Engine Exceptions will allow you to replace these kind of errors with exceptions.
Spaceship Operator - The Spaceship operator runs under the official name of Combined Comparison Operator. The notation of the new operator looks like this: <=> (kind of like a simplified spaceship, if you imagine it right). The spacehip operator returns 0 if both operands are equal, 1 if the left is greater, and -1 if the right is greater. It’s also called a three-way comparison operator, and it already exists in other popular programming languages like Perl and Ruby.
Null Coalescing Operators - The Null Coalescing operator is denoted with two question marks ( ?? ). You can use it when you want to check if something exists and return a default value, in case it doesn’t. The coalesce operator returns the result of its first operand if it exists and is not null, and the second operand in any other cases.
Accurate Type Declarations - the new PHP 7 enables developers to enhance the quality of their code with the help of return type declarations. PHP 7 introduces 4 new type declarations for scalar types: int, float, string and bool. The new scalar types allow developers to denote that they are expecting integers, floats, strings, or booleans to be returned.
Anonymous Classes - PHP 7 enables you to use anonymous classes, already a well-established practice in other object-oriented languages like C# and Java. An anonymous class is a class without a name. The object it instantiates has the same functionality as an object of a named class.
Cleans Up Deprecated - The goal of PHP 7 was to free up the space to enable improvement, so it was necessary to get rid of many deprecated functionalities and old and unsupported Server APIs and extensions. If you want to check which are these in detail, click here and here.