psalm/docs/running_psalm/checking_non_php_files.md

Checking non-PHP files

Psalm supports the ability to check various PHPish files by extending the FileChecker class. For example, if you have a template where the variables are set elsewhere, Psalm can scrape those variables and check the template with those variables pre-populated.

An example TemplateChecker is provided here.

To ensure your custom FileChecker is used, you must update the Psalm fileExtensions config in psalm.xml:

<fileExtensions>
    <extension name=".php" />
    <extension name=".phpt" checker="path/to/TemplateChecker.php" />
</fileExtensions>