Data Filtering

filter_has_var - Checks if variable of specified type exists
filter_id - Returns the filter ID belonging to a named filter
filter_input - Gets a specific external variable by name and optionally filters it
filter_input_array - Gets external variables and optionally filters them
filter_list - Returns a list of all supported filters
filter_var - Filters a variable with a specified filter
filter_var_array - Gets multiple variables and optionally filters them