You can discover and update HTML-specific Administration > General Settings > HTML.
PHP Code Analysis
SonarPHP and SonarHTML both analyze files with extensions:
File metrics, such as the number of lines of code, can only be measured by one of the languages, PHP or HTML. They are handled by SonarPHP by default, and by SonarHTML if for some reason SonarPHP is not present.
SonarHTML analyzes PHP files even if the PHP file extensions are not included in the list of file extensions to analyze.