public function sign($form = null) {
		$form = $form ?: $this->_context->form;

		if (isset($state[spl_object_hash($form)])) {
			return;
		}

		Filters::apply($form, 'create', function($params, $next) use ($form) {
			$this->_state[spl_object_hash($form)] = [
				'fields' => [],
				'locked' => [],
				'excluded' => []
			];
			return $next($params);
		});

		Filters::apply($form, 'end', function($params, $next) use ($form) {
			$id = spl_object_hash($form);

			if (!$this->_state[$id]) {
				return $next($params);
			}
			$formSignature = $this->_classes['formSignature'];

			$value = $formSignature::key($this->_state[$id]);
			echo $form->hidden('security.signature', compact('value'));

			$this->_state[$id] = [];
			return $next($params);
		});

		Filters::apply($form, '_defaults', function($params, $next) use ($form) {
			$defaults = [
				'locked' => ($params['method'] === 'hidden' && $params['name'] !== '_method'),
				'exclude' => $params['name'] === '_method'
			];
			$options = $params['options'];

			$options += $defaults;
			$params['options'] = array_diff_key($options, $defaults);
			$result = $next($params);

			if ($params['method'] === 'label') {
				return $result;
			}
			$value = isset($params['options']['value']) ? $params['options']['value'] : "";

			$type = [
				$options['exclude']  => 'excluded',
				!$options['exclude'] => 'fields',
				$options['locked']   => 'locked'
			];
			if (!$name = preg_replace('/(\.\d+)+$/', '', $params['name'])) {
				return $result;
			}
			$this->_state[spl_object_hash($form)][$type[true]][$name] = $value;
			return $result;
		});
	}
public function sign($form = null) {
		$form = $form ?: $this->_context->form;

		if (isset($state[spl_object_hash($form)])) {
			return;
		}

		Filters::apply($form, 'create', function($params, $next) use ($form) {
			$this->_state[spl_object_hash($form)] = [
				'fields' => [],
				'locked' => [],
				'excluded' => []
			];
			return $next($params);
		});

		Filters::apply($form, 'end', function($params, $next) use ($form) {
			$id = spl_object_hash($form);

			if (!$this->_state[$id]) {
				return $next($params);
			}
			$formSignature = $this->_classes['formSignature'];

			$value = $formSignature::key($this->_state[$id]);
			echo $form->hidden('security.signature', compact('value'));

			$this->_state[$id] = [];
			return $next($params);
		});

		Filters::apply($form, '_defaults', function($params, $next) use ($form) {
			$defaults = [
				'locked' => ($params['method'] === 'hidden' && $params['name'] !== '_method'),
				'exclude' => $params['name'] === '_method'
			];
			$options = $params['options'];

			$options += $defaults;
			$params['options'] = array_diff_key($options, $defaults);
			$result = $next($params);

			if ($params['method'] === 'label') {
				return $result;
			}
			$value = isset($params['options']['value']) ? $params['options']['value'] : "";

			$type = [
				$options['exclude']  => 'excluded',
				!$options['exclude'] => 'fields',
				$options['locked']   => 'locked'
			];
			if (!$name = preg_replace('/(\.\d+)+$/', '', $params['name'])) {
				return $result;
			}
			$this->_state[spl_object_hash($form)][$type[true]][$name] = $value;
			return $result;
		});
	}
public function sign ( $ form = null ) { $ form = $ form ? : $ this -> _context -> form ; if ( isset ( $ state [ spl_object_hash ( $ form ) ] ) ) { return ; } Filters :: apply ( $ form , 'create' , function ( $ params , $ next ) use ( $ form ) { $ this -> _state [ spl_object_hash ( $ form ) ] = [ 'fields' => [ ] , 'locked' => [ ] , 'excluded' => [ ] ] ; return $ next ( $ params ) ; } ) ; Filters :: apply ( $ form , 'end' , function ( $ params , $ next ) use ( $ form ) { $ id = spl_object_hash ( $ form ) ; if ( ! $ this -> _state [ $ id ] ) { return $ next ( $ params ) ; } $ formSignature = $ this -> _classes [ 'formSignature' ] ; $ value = $ formSignature :: key ( $ this -> _state [ $ id ] ) ; echo $ form -> hidden ( 'security.signature' , compact ( 'value' ) ) ; $ this -> _state [ $ id ] = [ ] ; return $ next ( $ params ) ; } ) ; Filters :: apply ( $ form , '_defaults' , function ( $ params , $ next ) use ( $ form ) { $ defaults = [ 'locked' => ( $ params [ 'method' ] === 'hidden' && $ params [ 'name' ] !== '_method' ) , 'exclude' => $ params [ 'name' ] === '_method' ] ; $ options = $ params [ 'options' ] ; $ options += $ defaults ; $ params [ 'options' ] = array_diff_key ( $ options , $ defaults ) ; $ result = $ next ( $ params ) ; if ( $ params [ 'method' ] === 'label' ) { return $ result ; } $ value = isset ( $ params [ 'options' ] [ 'value' ] ) ? $ params [ 'options' ] [ 'value' ] : "" ; $ type = [ $ options [ 'exclude' ] => 'excluded' , ! $ options [ 'exclude' ] => 'fields' , $ options [ 'locked' ] => 'locked' ] ; if ( ! $ name = preg_replace ( '/(\.\d+)+$/' , '' , $ params [ 'name' ] ) ) { return $ result ; } $ this -> _state [ spl_object_hash ( $ form ) ] [ $ type [ true ] ] [ $ name ] = $ value ; return $ result ; } ) ; }
Binds the `Security` helper to the `Form` helper to create a signature used to secure form
fields against tampering.

First `FormSignature` must be provided with a secret unique to your app. This is best
done in the bootstrap process. The secret key should be a random lengthy string.
```php
use lithium\security\validation\FormSignature;
FormSignature::config(['secret' => 'a long secret key']);
```

In the view call the `sign()` method before creating the form.
```php
<?php $this->security->sign(); ?>
<?=$this->form->create(...); ?>
// Form fields...
<?=$this->form->end(); ?>
```

In the corresponding controller action verify the signature.
```php
if ($this->request->is('post') && !FormSignature::check($this->request)) {
// The key didn't match, meaning the request has been tampered with.
}
```

Calling this method before a form is created adds two additional options to the `$options`
parameter in all form inputs:

- `'locked'` _boolean_: If `true`, _locks_ the value specified in the field when the field
is generated, such that tampering with the value will invalidate the signature. Defaults
to `true` for hidden fields, and `false` for all other form inputs.

- `'exclude'` _boolean_: If `true`, this field and all subfields of the same name will be
excluded from the signature calculation. This is useful in situations where fields may be
added dynamically on the client side. Defaults to `false`.

@see lithium\template\helper\Form
@see lithium\security\validation\FormSignature
@param object $form Optional. Allows specifying an instance of the `Form` helper manually.
@return void
Binds the Security helper to the Form helper to create a signature used to secure form fields against tampering .