diff --git a/examples.module b/examples.module
index 3e37702..d1836e2 100644
--- a/examples.module
+++ b/examples.module
@@ -50,6 +50,7 @@ function examples_toolbar() {
'field_example' => 'field_example.description',
'field_permission_example' => 'field_permission_example.description',
'file_example' => 'file_example.fileapi',
+ 'filter_example' => 'filter_example.page',
'hooks_example' => 'hooks_example.description',
'js_example' => 'js_example.info',
'menu_example' => 'examples.menu_example',
diff --git a/filter_example/filter_example.info.yml b/filter_example/filter_example.info.yml
new file mode 100644
index 0000000..38380ab
--- /dev/null
+++ b/filter_example/filter_example.info.yml
@@ -0,0 +1,9 @@
+name: 'Filter example'
+type: module
+description: 'An example module showing how to define a custom filter.'
+package: 'Example modules'
+core: 8.x
+dependencies:
+ - drupal:node
+ - drupal:filter
+ - examples:examples
diff --git a/filter_example/filter_example.links.menu.yml b/filter_example/filter_example.links.menu.yml
new file mode 100644
index 0000000..9a05863
--- /dev/null
+++ b/filter_example/filter_example.links.menu.yml
@@ -0,0 +1,4 @@
+filter_example.page:
+ title: 'Filter Example'
+ route_name: 'filter_example.page'
+ expanded: 'TRUE'
diff --git a/filter_example/filter_example.module b/filter_example/filter_example.module
new file mode 100644
index 0000000..0d6a327
--- /dev/null
+++ b/filter_example/filter_example.module
@@ -0,0 +1,38 @@
+, and replace it by the current time.
+ *
+ * Foo filter
+ *
+ * Drupal has several content formats (they are not filters), and in our example
+ * the each filter can be configured differently for each of the text formats
+ * where it is enabled. This example filter provides configuration that will
+ * allow an administrator to determine what string should be replaced with the
+ * text "foo".
+ *
+ * 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 HTML is escaped/stripped by other filters. But
+ * we want to use HTML in our result as well, and so 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.
+ *
+ * @see to \Drupal\filter\Plugin\FilterInterface
+ * @link https://www.drupal.org/docs/8/api/filter-api @endlink
+ */
diff --git a/filter_example/filter_example.routing.yml b/filter_example/filter_example.routing.yml
new file mode 100644
index 0000000..50658aa
--- /dev/null
+++ b/filter_example/filter_example.routing.yml
@@ -0,0 +1,7 @@
+filter_example.page:
+ path: '/examples/filter-example'
+ defaults:
+ _controller: '\Drupal\filter_example\Controller\FilterExampleController::description'
+ _title: 'Filter Example'
+ requirements:
+ _permission: 'access content'
diff --git a/filter_example/src/Controller/FilterExampleController.php b/filter_example/src/Controller/FilterExampleController.php
new file mode 100644
index 0000000..37442f2
--- /dev/null
+++ b/filter_example/src/Controller/FilterExampleController.php
@@ -0,0 +1,22 @@
+settings.
+ */
+ public function settingsForm(array $form, FormStateInterface $form_state) {
+ $form['filter_example_foo'] = [
+ '#type' => 'textfield',
+ '#title' => $this->t('Substitution string'),
+ '#default_value' => $this->settings['filter_example_foo'],
+ '#description' => $this->t('The string to substitute for "foo" everywhere in the text.'),
+ ];
+ return $form;
+ }
+
+ /**
+ * Foo filter process callback.
+ *
+ * The actual filtering is performed here. The supplied text should be
+ * returned once any necessary substitutions have taken place.
+ * The example just replaces foo with our custom defined string in
+ * the settings page.
+ */
+ public function process($text, $langcode) {
+ $replace = $this->settings['filter_example_foo'];
+ $new_text = str_replace('foo', $replace, $text);
+ return new FilterProcessResult($new_text);
+ }
+
+ /**
+ * Filter tips callback for foo filter.
+ *
+ * The tips callback allows filters to provide help text to users during the
+ * content editing process. Short tips are provided on the content editing
+ * screen, while long tips are provided on a separate linked page. Short tips
+ * are optional, but long tips are highly recommended.
+ */
+ public function tips($long = FALSE) {
+ $replacement = $this->settings['filter_example_foo'];
+ if (!$long) {
+ // This string will be shown in the content add/edit form.
+ return $this->t('%foo replaced with %replacement.', ['%foo' => 'foo', '%replacement' => $replacement]);
+ }
+ else {
+ return $this->t('Every instance of "foo" in the input text will be replaced with a configurable value. You can configure this value and put whatever you want there. The replacement value is "%replacement".', ['%replacement' => $replacement]);
+ }
+ }
+
+}
diff --git a/filter_example/src/Plugin/Filter/FilterTime.php b/filter_example/src/Plugin/Filter/FilterTime.php
new file mode 100644
index 0000000..7efc4aa
--- /dev/null
+++ b/filter_example/src/Plugin/Filter/FilterTime.php
@@ -0,0 +1,58 @@
+!', '[filter-example-time]', $text);
+ }
+
+ /**
+ * Time filter process callback.
+ *
+ * Now, in the "process" step, we'll search for our escaped time tags and
+ * do the real filtering: replace the xml tag with the date.
+ */
+ public function process($text, $langcode) {
+ $new_text = str_replace('[filter-example-time]', '' . format_date(time()) . '', $text);
+ return new FilterProcessResult($new_text);
+ }
+
+ /**
+ * Filter tips callback for time filter.
+ *
+ * The tips callback allows filters to provide help text to users during the
+ * content editing process. Short tips are provided on the content editing
+ * screen, while long tips are provided on a separate linked page. Short tips
+ * are optional, but long tips are highly recommended.
+ */
+ public function tips($long = FALSE) {
+ return $this->t('<time /> is replaced with the current time.');
+ }
+
+}
diff --git a/filter_example/templates/description.html.twig b/filter_example/templates/description.html.twig
new file mode 100644
index 0000000..e54cac8
--- /dev/null
+++ b/filter_example/templates/description.html.twig
@@ -0,0 +1,20 @@
+{#
+/**
+ * @file
+ * Contains the text of the filter_example explanation page
+ */
+#}
+
+{% set filter_admin_overview = path('filter.admin_overview') %}
+
+{% trans %}
+
This example provides two filters.
+
Foo Filter replaces "foo" with a configurable replacement.
+
Time Tag replaces the string "<time />" with the current time.
+
+To use these filters, go to admin/config/content/formats and edit whichever
+text format you're using to include these filters. You can include these filters by clicking on the checkboxes next to
+each of them. Make sure Time filter happens before 'Limit HTML tags' if not the "<time />" tag will be removed before
+being replaced.
+