Adds cookbook recipe for using input filters in forms

Signed-off-by: Frank Brückner <dev@froschdesignstudio.de>

docs/book/cookbook/input-filter-in-forms.md

@@ -0,0 +1,143 @@
+# Using Input Filters in Forms of laminas-form
+
+The following examples shows _two_ potential use cases of laminas-inputfilter within forms of [laminas-form](https://docs.laminas.dev/laminas-form/).
+
+## Define the Input Filter in a Form
+
+An input filter can be [defined directly in a form class](https://docs.laminas.dev/laminas-form/v3/quick-start/#hinting-to-the-input-filter) itself, using `Laminas\InputFilter\InputFilterProviderInterface`.
+This interface provides one method (`getInputFilterSpecification()`) that is used by a form of laminas-form to create an input filter.
+
+[Create a form as separate class](https://docs.laminas.dev/laminas-form/v3/quick-start/#factory-backed-form-extension) using the [`init` method](https://docs.laminas.dev/laminas-form/v3/advanced/#initialization), implement the interface `Laminas\InputFilter\InputFilterProviderInterface` and define the inputs via configuration array, e.g. `module/Album/src/Form/AlbumForm.php`:
+
+<!-- markdownlint-disable MD033 -->
+<pre class="language-php" data-line="7,10,26-48"><code>
+namespace Album\Form;
+
+use Laminas\Filter\StringTrim;
+use Laminas\Filter\StripTags;
+use Laminas\Form\Element\Text;
+use Laminas\Form\Form;
+use Laminas\InputFilter\InputFilterProviderInterface;
+use Laminas\Validator\StringLength;
+
+final class AlbumForm extends Form implements InputFilterProviderInterface
+{
+    public function init(): void
+    {
+        // Add form elements
+        $this->add([
+            'name'    => 'title',
+            'type'    => Text::class,
+            'options' => [
+                'label' => 'Title',
+            ],
+        ]);
+
+        // …
+    }
+
+    public function getInputFilterSpecification(): array
+    {
+        return [
+            // Add inputs
+            [
+                'name'    => 'title',
+                'filters' => [
+                    ['name' => StripTags::class],
+                    ['name' => StringTrim::class],
+                ],
+                'validators' => [
+                    [
+                        'name'    => StringLength::class,
+                        'options' => [
+                            'min' => 1,
+                            'max' => 100,
+                        ],
+                    ],
+                ],
+            ],
+            // …
+        ];
+    }
+}
+</code></pre>
+<!-- markdownlint-enable MD033 -->
+
+## Adding an Input Filter Defined as a Separate Class to a Form
+
+### Create Input Filter
+
+[Create an input filter as separate class](../intro.md), e.g. `module/Album/src/InputFilter/AlbumInputFilter.php`:
+
+```php
+namespace Album\InputFilter;
+
+use Laminas\Filter\StringTrim;
+use Laminas\Filter\StripTags;
+use Laminas\Validator\StringLength;
+use Laminas\InputFilter\InputFilter;
+
+final class AlbumInputFilter extends InputFilter
+{
+    public function init(): void
+    {
+        // Add inputs
+        $this->add(
+            [
+                'name'    => 'title',
+                'filters' => [
+                    ['name' => StripTags::class],
+                    ['name' => StringTrim::class],
+                ],
+                'validators' => [
+                    [
+                        'name'    => StringLength::class,
+                        'options' => [
+                            'min' => 1,
+                            'max' => 100,
+                        ],
+                    ],
+                ],
+            ]
+        );
+
+        // …
+    }
+}
+```
+
+### Create Form and Add Input Filter
+
+An input filter can be added directly in a form class itself, using the class name of the input filter or whatever name the input filter is registered under.
+
+Create a form as separate class using the `init` method and set the input filter via the `setInputFilterByName()` method of `Laminas\Form\Form`, e.g. `module/Album/src/Form/AlbumForm.php`:
+
+<!-- markdownlint-disable MD033 -->
+<pre class="language-php" data-line="11-12"><code>
+namespace Album\Form;
+
+use Album\InputFilter\AlbumInputFilter;
+use Laminas\Form\Element\Text;
+use Laminas\Form\Form;
+
+final class AlbumForm extends Form
+{
+    public function init(): void
+    {
+        // Set the input filter
+        $this->setInputFilterByName(AlbumInputFilter::class);
+
+        // Add form elements
+        $this->add([
+            'name'    => 'title',
+            'type'    => Text::class,
+            'options' => [
+                'label' => 'Title',
+            ],
+        ]);
+
+        // …
+    }
+}
+</code></pre>
+<!-- markdownlint-enable MD033 -->

mkdocs.yml

@@ -12,6 +12,8 @@ nav:
     - "Application Integration":
         - "Usage in a laminas-mvc application": application-integration/usage-in-a-laminas-mvc-application.md
         - "Usage in a mezzio application": application-integration/usage-in-a-mezzio-application.md
+    - Cookbook:
+        - "Using Input Filters in Forms of laminas-form": cookbook/input-filter-in-forms.md
 site_name: laminas-inputfilter
 site_description: 'Normalize and validate input sets from the web, APIs, the CLI, and more, including files.'
 repo_url: 'https://github.com/laminas/laminas-inputfilter'