Example: Filter

This example demonstrates how filters are created.

This is an example outlining how a module can define a filter that runs on user-submitted content before it is output on the browser.

To show all the capabilities of the filter system, we will define two filters in this module. One will substitute the string "foo" with an administratively-defined replacement string; the other one will replace a XML tag, <time />, with the current time.

Foo filter

Backdrop has several content formats (they are not filters). In our example the foo replacement can be configured for each one of them, allowing a HTML or PHP replacement. The module includes a settings callback, with options to configure that replacements. A tips callback will show the current replacement for the node that is edited.

Time filter.

This filter is a little trickier to implement than the previous one. Since the input involves special HTML characters (< and >), we have to run the filter before the HTML markup is escaped/stripped by other filters. We want to use HTML in our result as well; if we run this filter first, our replacement string could be escaped or stripped. The solution is to use the "prepare" operation to escape the special characters, and to later replace our escaped version in the "process" step.

Parent topics

File

modules/examples/filter_example/filter_example.module, line 7

Hook implementations for the Filter Example module.

Functions

Name	Location	Description
filter_example_filter_info	modules/examples/filter_example/filter_example.module	Implements hook_filter_info().
filter_example_menu	modules/examples/filter_example/filter_example.module	Implements hook_menu().
_filter_example_filter_foo_process	modules/examples/filter_example/filter_example.module	Foo filter process callback.
_filter_example_filter_foo_settings	modules/examples/filter_example/filter_example.module	Settings callback for foo filter.
_filter_example_filter_foo_tips	modules/examples/filter_example/filter_example.module	Filter tips callback for foo filter.
_filter_example_filter_time_prepare	modules/examples/filter_example/filter_example.module	Time filter prepare callback.
_filter_example_filter_time_process	modules/examples/filter_example/filter_example.module	Time filter process callback.
_filter_example_filter_time_tips	modules/examples/filter_example/filter_example.module	Filter tips callback for time filter.
_filter_example_information	modules/examples/filter_example/filter_example.module	Simply returns a little bit of information about the example.