Actually this is the version that supports checks

src/Abstract_/Form.php

@@ -74,8 +74,8 @@ public function getSingleControlTemplate() {
      * @return boolean
      */
     public function dataValid() {
-        foreach (new \RecursiveIteratorIterator($this) as $child) {
-            if ($child instanceof Abstract_\FormElement && !$child->dataValid()) {
+        foreach (new \RecursiveIteratorIterator($this, \RecursiveIteratorIterator::SELF_FIRST) as $child) {
+            if ($child instanceof FormElement && !$child->dataValid()) {
                 return false;
             }
         }

src/Abstract_/FormElement.php

@@ -34,10 +34,9 @@ public function getForm() {
         if ($this->existsInheritableAppendage('_FORM'))
             return $this->getInheritableAppendage('_FORM');
         else {
-            #print_r(debug_backtrace(DEBUG_BACKTRACE_IGNORE_ARGS));
-
             throw new exception\NotLazyEnough(
-            'No Form for FormElement found. Maybe not yet a child of a Form.');
+            'No Form for FormElement found. Maybe not yet a child of a Form.'
+            );
         }
     }
 
@@ -59,4 +58,8 @@ public function getHtmlName(array $extraKeys = []) {
                 '_' . $this->getName() . implode('_', $extraKeys);
     }
 
+    public function getValueUser() {
+        return $this->getForm()->getValueUser($this->getHtmlName());
+    }
+
 }

src/Abstract_/FormField.php

@@ -17,10 +17,29 @@ public function changed() {
 
     /**
      * 
-     * @todo not implemented
      */
     public function dataValid() {
-        return true;
+        $allValid = true;
+        foreach ($this->checks as $key => $check) {
+            $valid = $check($this->getValueUser());
+            $allValid = $allValid && $valid;
+        }
+
+        return $allValid;
+    }
+
+    /**
+     *
+     * @var array[Check]
+     */
+    public $checks = [];
+
+    /**
+     * 
+     * @param Check $check
+     */
+    public function addValidityCheck(\hemio\form\Check $check) {
+        $this->checks[$check->getId()] = $check;
     }
 
 }

src/Abstract_/FormFieldDefault.php

@@ -74,14 +74,6 @@ public function getValueToUse() {
             return $this->getValueDefault();
     }
 
-    public function getValueUser() {
-        $value = $this->getForm()->getValueUser($this->getHtmlName());
-        if ($value === null)
-            return null;
-        else
-            return $this->getFiltered($value);
-    }
-
     public function getValueStored() {
         return $this->getFiltered(
                         $this->getForm()->getValueStored($this->getName()));
@@ -140,4 +132,10 @@ public function __toString() {
     }
 
     abstract public function fill();
+
+    public function setForm(Form $form) {
+        $this->control->setAttribute('form', $form->getHtmlName());
+        $this->addInheritableAppendage('_FORM', $form);
+    }
+
 }

src/Abstract_/FormFieldInput.php

@@ -66,8 +66,6 @@ public function fill() {
         return $template;
     }
 
-
-
     public function describe() {
         return sprint('INPUT(%s)', strtoupper($this->getInputType()));
     }

src/Check.php

@@ -0,0 +1,72 @@
+<?php
+
+/*
+ * Copyright (C) 2015 Michael Herold <quabla@hemio.de>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+namespace hemio\form;
+
+/**
+ * Description of ValidityCheck
+ *
+ * @author Michael Herold <quabla@hemio.de>
+ */
+abstract class Check {
+
+    /**
+     *
+     * @var string
+     */
+    protected $id;
+
+    /**
+     *
+     * @var callable
+     */
+    protected $check;
+
+    /**
+     *
+     * @var string
+     */
+    protected $message;
+
+    /**
+     * @return string Id
+     */
+    public function getId() {
+        return $this->id;
+    }
+
+    /**
+     * 
+     * @return string
+     */
+    public function getMessage() {
+        return $this->message;
+    }
+
+    /**
+     * 
+     * @param mixed $value
+     * @return boolean
+     */
+    public function check($value) {
+        $check = $this->check;
+        return $check($value);
+    }
+
+}

src/CheckCustom.php

@@ -0,0 +1,35 @@
+<?php
+
+/*
+ * Copyright (C) 2015 Michael Herold <quabla@hemio.de>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+namespace hemio\form;
+
+/**
+ * Description of CheckCustom
+ *
+ * @author Michael Herold <quabla@hemio.de>
+ */
+class CheckCustom extends Check {
+
+    public function __construct($id, callable $check, $message = null) {
+        $this->id = $id;
+        $this->check = $check;
+        $this->message = $message;
+    }
+
+}

src/CheckMaxLength.php

@@ -0,0 +1,40 @@
+<?php
+
+/*
+ * Copyright (C) 2015 Michael Herold <quabla@hemio.de>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+namespace hemio\form;
+
+/**
+ * Description of CheckLength
+ *
+ * @author Michael Herold <quabla@hemio.de>
+ */
+class CheckMaxLength extends Check {
+
+    protected $maxLength;
+
+    public function __construct($maxLength) {
+        $this->maxLength = $maxLength;
+        $this->check = $this;
+    }
+
+    public function __invoke($value) {
+        return strlen($value) <= $this->maxLength;
+    }
+
+}

src/CheckMinLength.php

@@ -0,0 +1,40 @@
+<?php
+
+/*
+ * Copyright (C) 2015 Michael Herold <quabla@hemio.de>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+namespace hemio\form;
+
+/**
+ * Description of CheckMinLength
+ *
+ * @author Michael Herold <quabla@hemio.de>
+ */
+class CheckMinLength extends Check {
+
+    protected $minLength;
+
+    public function __construct($maxLength) {
+        $this->minLength = $maxLength;
+        $this->check = $this;
+    }
+
+    public function __invoke($value) {
+        return strlen($value) >= $this->minLength;
+    }
+
+}

src/FieldEmail.php

@@ -11,7 +11,7 @@ public function getInputType() {
         return 'email';
     }
 
-    public function inputValid() {
+    public function inputValidOld() {
         $strAddress = $this->getValueUser($this->getHtmlName());
 
         $arrExplode = explode('@', $strAddress);

src/FieldPassword.php

@@ -13,7 +13,7 @@ public function getValueStored() {
         return '';
     }
 
-    public function getValueUser() {
+    public function getValueToUse() {
         return '';
     }
 

src/FieldSelect.php

@@ -50,8 +50,20 @@ public function fill() {
         return $template;
     }
 
-    public function addOption($value, $content) {
-        $this->getControlElement()->addChild(new html\Option($value, new html\String($content)));
+    /**
+     * 
+     * @param mixed $value
+     * @param mixed $content
+     * @return html\Option
+     */
+    public function addOption($value, $content = null) {
+        if ($content === null)
+            $content = $value;
+
+        $option = new html\Option($value, new html\String($content));
+        $this->getControlElement()->addChild($option);
+
+        return $option;
     }
 
 }

src/FieldText.php

@@ -6,7 +6,6 @@
 
 class FieldText extends Abstract_\FormFieldInput {
 
-
     public function getInputType() {
         return 'text';
     }
@@ -23,18 +22,16 @@ public function setPlaceholder($placeholder) {
      * 
      * @param boolean $allow
      */
-    public function setAllowMultiple($allow) {
+    public function setAllowMultiple($allow = true) {
         $this->getControlElement()->setAttribute('multiple', (boolean) $allow);
     }
 
     /**
      * 
      * @param boolean $required
      */
-    public function setIsRequired($required) {
+    public function setRequired($required = true) {
         $this->getControlElement()->setAttribute('required', (boolean) $required);
     }
 
-
-
 }

src/FormPost.php

@@ -11,16 +11,18 @@ class FormPost extends Abstract_\Form {
 
     public function __construct($name, array $post = null, array $get = null, array $stored = []) {
         parent::__construct($name, $post, $get, $stored);
-        $this->addChild(new InputHidden($this->getIdentifierName(), ''));
+
+        $this['form_identifier'] = new InputHidden($this->getIdentifierName(), '');
+
         $this->setAttribute('method', 'post');
     }
 
     public function submitted() {
-        return $this->getPost($this->getIdentifierName()) !== null;
+        return $this['form_identifier']->getValueUser() !== null;
     }
 
     public function getIdentifierName() {
-        return $this->name . '___form_identifier';
+        return '__form_identifier';
     }
 
     public function correctSubmitted() {

src/InputHidden.php

@@ -13,7 +13,6 @@ public function __construct($name, $value) {
         $this->name = $name;
 
         $this['INPUT'] = new html\Input('hidden');
-        $this['INPUT']->setAttribute('type', 'hidden');
         $this['INPUT']->setAttribute('value', $value);
     }