Collision free approach to resolve the DOM ID issue in a clean way. Fix to generation of ids for multiple checkboxes. Resolves ticket 4064.

lib/Cake/Test/Case/View/Helper/FormHelperTest.php

@@ -3222,8 +3222,8 @@ class FormHelperTest extends CakeTestCase {
 		$expected = array(
 			'input' => array('type' => 'hidden', 'name' => 'data[Model][multi_field]', 'value' => '', 'id' => 'ModelMultiField'),
 			array('div' => array('class' => 'checkbox')),
-			array('input' => array('type' => 'checkbox', 'name' => 'data[Model][multi_field][]', 'value' => '1/2', 'id' => 'ModelMultiField12')),
-			array('label' => array('for' => 'ModelMultiField12')),
+			array('input' => array('type' => 'checkbox', 'name' => 'data[Model][multi_field][]', 'value' => '1/2', 'id' => 'ModelMultiField1/2')),
+			array('label' => array('for' => 'ModelMultiField1/2')),
 			'half',
 			'/label',
 			'/div',
@@ -4151,6 +4151,50 @@ class FormHelperTest extends CakeTestCase {
 	}
 
 /**
+ * testDomIdSuffix method
+ *
+ * @return void
+ */
+	public function testDomIdSuffix() {
+		$result = $this->Form->domIdSuffix('1 string with 1$-dollar signs');
+		$this->assertEquals('1StringWith1$-dollarSigns', $result);
+
+		$result = $this->Form->domIdSuffix('<abc x="foo" y=\'bar\'>');
+		$this->assertEquals('AbcX=FooY=Bar', $result);
+
+		$result = $this->Form->domIdSuffix('1 string with 1$-dollar signs', 'xhtml');
+		$this->assertEquals('1StringWith1-dollarSigns', $result);
+
+		$result = $this->Form->domIdSuffix('<abc x="foo" y=\'bar\'>', 'xhtml');
+		$this->assertEquals('AbcXFooYBar', $result);
+	}
+
+/**
+ * testDomIdSuffixCollisionResolvement()
+ *
+ * @return void
+ */
+	public function testDomIdSuffixCollisionResolvement() {
+		$result = $this->Form->domIdSuffix('a>b');
+		$this->assertEquals('AB', $result);
+
+		$result = $this->Form->domIdSuffix('a<b');
+		$this->assertEquals('AB1', $result);
+
+		$result = $this->Form->domIdSuffix('a\'b');
+		$this->assertEquals('AB2', $result);
+
+		$result = $this->Form->domIdSuffix('1 string with 1$-dollar', 'xhtml');
+		$this->assertEquals('1StringWith1-dollar', $result);
+
+		$result = $this->Form->domIdSuffix('1 string with 1€-dollar', 'xhtml');
+		$this->assertEquals('1StringWith1-dollar1', $result);
+
+		$result = $this->Form->domIdSuffix('1 string with 1$-dollar', 'xhtml');
+		$this->assertEquals('1StringWith1-dollar2', $result);
+	}
+
+/**
  * testSelect method
  *
  * Test select element generation.
@@ -4998,6 +5042,84 @@ class FormHelperTest extends CakeTestCase {
 			'/div'
 		);
 		$this->assertTags($result, $expected);
+
+		$result = $this->Form->select(
+			'Model.multi_field',
+			array('a+' => 'first', 'a++' => 'second', 'a+++' => 'third'),
+			array('multiple' => 'checkbox')
+		);
+		$expected = array(
+			'input' => array(
+				'type' => 'hidden', 'name' => 'data[Model][multi_field]', 'value' => '', 'id' => 'ModelMultiField'
+			),
+			array('div' => array('class' => 'checkbox')),
+			array('input' => array(
+				'type' => 'checkbox', 'name' => 'data[Model][multi_field][]',
+				'value' => 'a+', 'id' => 'ModelMultiFieldA+'
+			)),
+			array('label' => array('for' => 'ModelMultiFieldA+')),
+			'first',
+			'/label',
+			'/div',
+			array('div' => array('class' => 'checkbox')),
+			array('input' => array(
+				'type' => 'checkbox', 'name' => 'data[Model][multi_field][]',
+				'value' => 'a++', 'id' => 'ModelMultiFieldA++'
+			)),
+			array('label' => array('for' => 'ModelMultiFieldA++')),
+			'second',
+			'/label',
+			'/div',
+			array('div' => array('class' => 'checkbox')),
+			array('input' => array(
+				'type' => 'checkbox', 'name' => 'data[Model][multi_field][]',
+				'value' => 'a+++', 'id' => 'ModelMultiFieldA+++'
+			)),
+			array('label' => array('for' => 'ModelMultiFieldA+++')),
+			'third',
+			'/label',
+			'/div'
+		);
+		$this->assertTags($result, $expected);
+
+		$result = $this->Form->select(
+			'Model.multi_field',
+			array('a>b' => 'first', 'a<b' => 'second', 'a"b' => 'third'),
+			array('multiple' => 'checkbox')
+		);
+		$expected = array(
+			'input' => array(
+				'type' => 'hidden', 'name' => 'data[Model][multi_field]', 'value' => '', 'id' => 'ModelMultiField'
+			),
+			array('div' => array('class' => 'checkbox')),
+			array('input' => array(
+				'type' => 'checkbox', 'name' => 'data[Model][multi_field][]',
+				'value' => 'a&gt;b', 'id' => 'ModelMultiFieldAB2'
+			)),
+			array('label' => array('for' => 'ModelMultiFieldAB2')),
+			'first',
+			'/label',
+			'/div',
+			array('div' => array('class' => 'checkbox')),
+			array('input' => array(
+				'type' => 'checkbox', 'name' => 'data[Model][multi_field][]',
+				'value' => 'a&lt;b', 'id' => 'ModelMultiFieldAB1'
+			)),
+			array('label' => array('for' => 'ModelMultiFieldAB1')),
+			'second',
+			'/label',
+			'/div',
+			array('div' => array('class' => 'checkbox')),
+			array('input' => array(
+				'type' => 'checkbox', 'name' => 'data[Model][multi_field][]',
+				'value' => 'a&quot;b', 'id' => 'ModelMultiFieldAB'
+			)),
+			array('label' => array('for' => 'ModelMultiFieldAB')),
+			'third',
+			'/label',
+			'/div'
+		);
+		$this->assertTags($result, $expected);
 	}
 
 /**

lib/Cake/Test/Case/View/HelperTest.php

@@ -852,6 +852,16 @@ class HelperTest extends CakeTestCase {
 	}
 
 /**
+ * testDomId method
+ *
+ * @return void
+ */
+	public function testDomId() {
+		$result = $this->Helper->domId('Foo.bar');
+		$this->assertEquals('FooBar', $result);
+	}
+
+/**
  * testMultiDimensionalField method
  *
  * @return void

lib/Cake/View/Helper.php

@@ -16,6 +16,7 @@
 
 App::uses('Router', 'Routing');
 App::uses('Hash', 'Utility');
+App::uses('Inflector', 'Utility');
 
 /**
  * Abstract base class for all other Helpers in CakePHP.

lib/Cake/View/Helper/FormHelper.php

@@ -17,6 +17,7 @@
 App::uses('ClassRegistry', 'Utility');
 App::uses('AppHelper', 'View/Helper');
 App::uses('Hash', 'Utility');
+App::uses('Inflector', 'Utility');
 
 /**
  * Form helper library.
@@ -110,6 +111,13 @@ class FormHelper extends AppHelper {
 	public $validationErrors = array();
 
 /**
+ * Holds already used DOM ID suffixes to avoid collisions with multiple form field elements.
+ *
+ * @var array
+ */
+	protected $_domIdSuffixes = array();
+
+/**
  * Copies the validationErrors variable from the View object into this instance
  *
  * @param View $View The View this helper is being attached to.
@@ -2066,6 +2074,34 @@ class FormHelper extends AppHelper {
 	}
 
 /**
+ * Generates a valid DOM ID suffix from a string.
+ * Also avoids collisions when multiple values are coverted to the same suffix by
+ * appending a numeric value.
+ *
+ * For pre-HTML5 IDs only characters like a-z 0-9 - _ are valid. HTML5 doesn't have that
+ * limitation, but to avoid layout issues it still filters out some sensitive chars.
+ *
+ * @param string $value The value that should be transferred into a DOM ID suffix.
+ * @param string $type Doctype to use. Defaults to html5. Anything else will use limited chars.
+ * @return string DOM ID
+ */
+	public function domIdSuffix($value, $type = 'html5') {
+		if ($type === 'html5') {
+			$value = str_replace(array('<', '>', ' ', '"', '\''), '_', $value);
+		} else {
+			$value = preg_replace('~[^\\pL\d-_]+~u', '_', $value);
+		}
+		$value = Inflector::camelize($value);
+		$count = 1;
+		$suffix = $value;
+		while (in_array($suffix, $this->_domIdSuffixes)) {
+			$suffix = $value . $count++;
+		}
+		$this->_domIdSuffixes[] = $suffix;
+		return $suffix;
+	}
+
+/**
  * Returns a SELECT element for days.
  *
  * ### Attributes:
@@ -2609,6 +2645,7 @@ class FormHelper extends AppHelper {
 		$selectedIsEmpty = ($attributes['value'] === '' || $attributes['value'] === null);
 		$selectedIsArray = is_array($attributes['value']);
 
+		$this->_domIdSuffixes = array();
 		foreach ($elements as $name => $title) {
 			$htmlOptions = array();
 			if (is_array($title) && (!isset($title['name']) || !isset($title['value']))) {
@@ -2677,7 +2714,7 @@ class FormHelper extends AppHelper {
 					if ($attributes['style'] === 'checkbox') {
 						$htmlOptions['value'] = $name;
 
-						$tagName = $attributes['id'] . Inflector::camelize(Inflector::slug($name));
+						$tagName = $attributes['id'] . $this->domIdSuffix($name);
 						$htmlOptions['id'] = $tagName;
 						$label = array('for' => $tagName);