What are some popular PHP template engines and how do you install them?

Popular PHP template engines include Twig, Smarty, Blade, and Plates. To install these template engines, you typically need to use a package manager like Composer. You can add the template engine as a dependency in your project's `composer.json` file and then run `composer install` to download and install the template engine. Example: ```json { "require": { "twig/twig": "^3.0" } } ``` After adding the dependency in your `composer.json` file, run `composer install` in your project directory to install Twig.