The preferred way to install this extension is through composer.
Either run
php composer.phar require cinghie/yii2-simplehtmldom "@dev"
or add
"cinghie/yii2-simplehtmldom": "@dev"
to the require section of your composer.json file.
use cinghie\simplehtmldom\SimpleHtmlDom;
SimpleHtmlDom::file_get_html('http://www.google.com');
SimpleHtmlDom::str_get_html($string);