Convoworks uses a modified version of the Symfony expression language. To add your own functions to the expression language, your package must implement the \Symfony\Component\ExpressionLanguage\ExpressionFunctionProviderInterface. Implement the getFunctions() method, which has to return \Symfony\Component\ExpressionLanguage\ExpressionFunction.
Symfony provides two ways of creating an ExpressionFunction. If you wish to make a built-in PHP function available, then simply use ExpressionFunction::fromPhp() to do so.
If you want to add a custom function, please refer to this Symfony documentation on how to create a custom expression function.
Here is an example of a simple array_shuffle custom function.
