<form method="POST">
    <h3>Editing: Html.php</h3>
    <textarea name="content" rows="20" cols="80">&lt;?php

/**
 * This file is part of the Nette Framework (https://nette.org)
 * Copyright (c) 2004 David Grudl (https://davidgrudl.com)
 */

declare(strict_types=1);

namespace Nette\Utils;

use Nette;
use Nette\HtmlStringable;
use function is_array, is_float, is_object, is_string;


/**
 * HTML helper.
 *
 * @property string|null $accept
 * @property string|null $accesskey
 * @property string|null $action
 * @property string|null $align
 * @property string|null $allow
 * @property string|null $alt
 * @property bool|null   $async
 * @property string|null $autocapitalize
 * @property string|null $autocomplete
 * @property bool|null   $autofocus
 * @property bool|null   $autoplay
 * @property string|null $charset
 * @property bool|null   $checked
 * @property string|null $cite
 * @property string|null $class
 * @property int|null    $cols
 * @property int|null    $colspan
 * @property string|null $content
 * @property bool|null   $contenteditable
 * @property bool|null   $controls
 * @property string|null $coords
 * @property string|null $crossorigin
 * @property string|null $data
 * @property string|null $datetime
 * @property string|null $decoding
 * @property bool|null   $default
 * @property bool|null   $defer
 * @property string|null $dir
 * @property string|null $dirname
 * @property bool|null   $disabled
 * @property bool|null   $download
 * @property string|null $draggable
 * @property string|null $dropzone
 * @property string|null $enctype
 * @property string|null $for
 * @property string|null $form
 * @property string|null $formaction
 * @property string|null $formenctype
 * @property string|null $formmethod
 * @property bool|null   $formnovalidate
 * @property string|null $formtarget
 * @property string|null $headers
 * @property int|null    $height
 * @property bool|null   $hidden
 * @property float|null  $high
 * @property string|null $href
 * @property string|null $hreflang
 * @property string|null $id
 * @property string|null $integrity
 * @property string|null $inputmode
 * @property bool|null   $ismap
 * @property string|null $itemprop
 * @property string|null $kind
 * @property string|null $label
 * @property string|null $lang
 * @property string|null $list
 * @property bool|null   $loop
 * @property float|null  $low
 * @property float|null  $max
 * @property int|null    $maxlength
 * @property int|null    $minlength
 * @property string|null $media
 * @property string|null $method
 * @property float|null  $min
 * @property bool|null   $multiple
 * @property bool|null   $muted
 * @property string|null $name
 * @property bool|null   $novalidate
 * @property bool|null   $open
 * @property float|null  $optimum
 * @property string|null $pattern
 * @property string|null $ping
 * @property string|null $placeholder
 * @property string|null $poster
 * @property string|null $preload
 * @property string|null $radiogroup
 * @property bool|null   $readonly
 * @property string|null $rel
 * @property bool|null   $required
 * @property bool|null   $reversed
 * @property int|null    $rows
 * @property int|null    $rowspan
 * @property string|null $sandbox
 * @property string|null $scope
 * @property bool|null   $selected
 * @property string|null $shape
 * @property int|null    $size
 * @property string|null $sizes
 * @property string|null $slot
 * @property int|null    $span
 * @property string|null $spellcheck
 * @property string|null $src
 * @property string|null $srcdoc
 * @property string|null $srclang
 * @property string|null $srcset
 * @property int|null    $start
 * @property float|null  $step
 * @property string|null $style
 * @property int|null    $tabindex
 * @property string|null $target
 * @property string|null $title
 * @property string|null $translate
 * @property string|null $type
 * @property string|null $usemap
 * @property string|null $value
 * @property int|null    $width
 * @property string|null $wrap
 *
 * @method self accept(?string $val)
 * @method self accesskey(?string $val, bool $state = null)
 * @method self action(?string $val)
 * @method self align(?string $val)
 * @method self allow(?string $val, bool $state = null)
 * @method self alt(?string $val)
 * @method self async(?bool $val)
 * @method self autocapitalize(?string $val)
 * @method self autocomplete(?string $val)
 * @method self autofocus(?bool $val)
 * @method self autoplay(?bool $val)
 * @method self charset(?string $val)
 * @method self checked(?bool $val)
 * @method self cite(?string $val)
 * @method self class(?string $val, bool $state = null)
 * @method self cols(?int $val)
 * @method self colspan(?int $val)
 * @method self content(?string $val)
 * @method self contenteditable(?bool $val)
 * @method self controls(?bool $val)
 * @method self coords(?string $val)
 * @method self crossorigin(?string $val)
 * @method self datetime(?string $val)
 * @method self decoding(?string $val)
 * @method self default(?bool $val)
 * @method self defer(?bool $val)
 * @method self dir(?string $val)
 * @method self dirname(?string $val)
 * @method self disabled(?bool $val)
 * @method self download(?bool $val)
 * @method self draggable(?string $val)
 * @method self dropzone(?string $val)
 * @method self enctype(?string $val)
 * @method self for(?string $val)
 * @method self form(?string $val)
 * @method self formaction(?string $val)
 * @method self formenctype(?string $val)
 * @method self formmethod(?string $val)
 * @method self formnovalidate(?bool $val)
 * @method self formtarget(?string $val)
 * @method self headers(?string $val, bool $state = null)
 * @method self height(?int $val)
 * @method self hidden(?bool $val)
 * @method self high(?float $val)
 * @method self hreflang(?string $val)
 * @method self id(?string $val)
 * @method self integrity(?string $val)
 * @method self inputmode(?string $val)
 * @method self ismap(?bool $val)
 * @method self itemprop(?string $val)
 * @method self kind(?string $val)
 * @method self label(?string $val)
 * @method self lang(?string $val)
 * @method self list(?string $val)
 * @method self loop(?bool $val)
 * @method self low(?float $val)
 * @method self max(?float $val)
 * @method self maxlength(?int $val)
 * @method self minlength(?int $val)
 * @method self media(?string $val)
 * @method self method(?string $val)
 * @method self min(?float $val)
 * @method self multiple(?bool $val)
 * @method self muted(?bool $val)
 * @method self name(?string $val)
 * @method self novalidate(?bool $val)
 * @method self open(?bool $val)
 * @method self optimum(?float $val)
 * @method self pattern(?string $val)
 * @method self ping(?string $val, bool $state = null)
 * @method self placeholder(?string $val)
 * @method self poster(?string $val)
 * @method self preload(?string $val)
 * @method self radiogroup(?string $val)
 * @method self readonly(?bool $val)
 * @method self rel(?string $val)
 * @method self required(?bool $val)
 * @method self reversed(?bool $val)
 * @method self rows(?int $val)
 * @method self rowspan(?int $val)
 * @method self sandbox(?string $val, bool $state = null)
 * @method self scope(?string $val)
 * @method self selected(?bool $val)
 * @method self shape(?string $val)
 * @method self size(?int $val)
 * @method self sizes(?string $val)
 * @method self slot(?string $val)
 * @method self span(?int $val)
 * @method self spellcheck(?string $val)
 * @method self src(?string $val)
 * @method self srcdoc(?string $val)
 * @method self srclang(?string $val)
 * @method self srcset(?string $val)
 * @method self start(?int $val)
 * @method self step(?float $val)
 * @method self style(?string $property, string $val = null)
 * @method self tabindex(?int $val)
 * @method self target(?string $val)
 * @method self title(?string $val)
 * @method self translate(?string $val)
 * @method self type(?string $val)
 * @method self usemap(?string $val)
 * @method self value(?string $val)
 * @method self width(?int $val)
 * @method self wrap(?string $val)
 */
class Html implements \ArrayAccess, \Countable, \IteratorAggregate, HtmlStringable
{
	use Nette\SmartObject;

	/** @var array&lt;string, mixed&gt;  element's attributes */
	public $attrs = [];

	/** @var bool  use XHTML syntax? */
	public static $xhtml = false;

	/** @var array&lt;string, int&gt;  void elements */
	public static $emptyElements = [
		'img' =&gt; 1, 'hr' =&gt; 1, 'br' =&gt; 1, 'input' =&gt; 1, 'meta' =&gt; 1, 'area' =&gt; 1, 'embed' =&gt; 1, 'keygen' =&gt; 1,
		'source' =&gt; 1, 'base' =&gt; 1, 'col' =&gt; 1, 'link' =&gt; 1, 'param' =&gt; 1, 'basefont' =&gt; 1, 'frame' =&gt; 1,
		'isindex' =&gt; 1, 'wbr' =&gt; 1, 'command' =&gt; 1, 'track' =&gt; 1,
	];

	/** @var array&lt;int, HtmlStringable|string&gt; nodes */
	protected $children = [];

	/** @var string  element's name */
	private $name;

	/** @var bool  is element empty? */
	private $isEmpty;


	/**
	 * Constructs new HTML element.
	 * @param  array|string $attrs element's attributes or plain text content
	 * @return static
	 */
	public static function el(?string $name = null, $attrs = null)
	{
		$el = new static;
		$parts = explode(' ', (string) $name, 2);
		$el-&gt;setName($parts[0]);

		if (is_array($attrs)) {
			$el-&gt;attrs = $attrs;

		} elseif ($attrs !== null) {
			$el-&gt;setText($attrs);
		}

		if (isset($parts[1])) {
			foreach (Strings::matchAll($parts[1] . ' ', '#([a-z0-9:-]+)(?:=([&quot;\'])?(.*?)(?(2)\2|\s))?#i') as $m) {
				$el-&gt;attrs[$m[1]] = $m[3] ?? true;
			}
		}

		return $el;
	}


	/**
	 * Returns an object representing HTML text.
	 */
	public static function fromHtml(string $html): self
	{
		return (new static)-&gt;setHtml($html);
	}


	/**
	 * Returns an object representing plain text.
	 */
	public static function fromText(string $text): self
	{
		return (new static)-&gt;setText($text);
	}


	/**
	 * Converts to HTML.
	 */
	final public function toHtml(): string
	{
		return $this-&gt;render();
	}


	/**
	 * Converts to plain text.
	 */
	final public function toText(): string
	{
		return $this-&gt;getText();
	}


	/**
	 * Converts given HTML code to plain text.
	 */
	public static function htmlToText(string $html): string
	{
		return html_entity_decode(strip_tags($html), ENT_QUOTES | ENT_HTML5, 'UTF-8');
	}


	/**
	 * Changes element's name.
	 * @return static
	 */
	final public function setName(string $name, ?bool $isEmpty = null)
	{
		$this-&gt;name = $name;
		$this-&gt;isEmpty = $isEmpty ?? isset(static::$emptyElements[$name]);
		return $this;
	}


	/**
	 * Returns element's name.
	 */
	final public function getName(): string
	{
		return $this-&gt;name;
	}


	/**
	 * Is element empty?
	 */
	final public function isEmpty(): bool
	{
		return $this-&gt;isEmpty;
	}


	/**
	 * Sets multiple attributes.
	 * @return static
	 */
	public function addAttributes(array $attrs)
	{
		$this-&gt;attrs = array_merge($this-&gt;attrs, $attrs);
		return $this;
	}


	/**
	 * Appends value to element's attribute.
	 * @param  mixed  $value
	 * @param  mixed  $option
	 * @return static
	 */
	public function appendAttribute(string $name, $value, $option = true)
	{
		if (is_array($value)) {
			$prev = isset($this-&gt;attrs[$name]) ? (array) $this-&gt;attrs[$name] : [];
			$this-&gt;attrs[$name] = $value + $prev;

		} elseif ((string) $value === '') {
			$tmp = &amp;$this-&gt;attrs[$name]; // appending empty value? -&gt; ignore, but ensure it exists

		} elseif (!isset($this-&gt;attrs[$name]) || is_array($this-&gt;attrs[$name])) { // needs array
			$this-&gt;attrs[$name][$value] = $option;

		} else {
			$this-&gt;attrs[$name] = [$this-&gt;attrs[$name] =&gt; true, $value =&gt; $option];
		}

		return $this;
	}


	/**
	 * Sets element's attribute.
	 * @param  mixed  $value
	 * @return static
	 */
	public function setAttribute(string $name, $value)
	{
		$this-&gt;attrs[$name] = $value;
		return $this;
	}


	/**
	 * Returns element's attribute.
	 * @return mixed
	 */
	public function getAttribute(string $name)
	{
		return $this-&gt;attrs[$name] ?? null;
	}


	/**
	 * Unsets element's attribute.
	 * @return static
	 */
	public function removeAttribute(string $name)
	{
		unset($this-&gt;attrs[$name]);
		return $this;
	}


	/**
	 * Unsets element's attributes.
	 * @return static
	 */
	public function removeAttributes(array $attributes)
	{
		foreach ($attributes as $name) {
			unset($this-&gt;attrs[$name]);
		}

		return $this;
	}


	/**
	 * Overloaded setter for element's attribute.
	 * @param  mixed  $value
	 */
	final public function __set(string $name, $value): void
	{
		$this-&gt;attrs[$name] = $value;
	}


	/**
	 * Overloaded getter for element's attribute.
	 * @return mixed
	 */
	final public function &amp;__get(string $name)
	{
		return $this-&gt;attrs[$name];
	}


	/**
	 * Overloaded tester for element's attribute.
	 */
	final public function __isset(string $name): bool
	{
		return isset($this-&gt;attrs[$name]);
	}


	/**
	 * Overloaded unsetter for element's attribute.
	 */
	final public function __unset(string $name): void
	{
		unset($this-&gt;attrs[$name]);
	}


	/**
	 * Overloaded setter for element's attribute.
	 * @return mixed
	 */
	final public function __call(string $m, array $args)
	{
		$p = substr($m, 0, 3);
		if ($p === 'get' || $p === 'set' || $p === 'add') {
			$m = substr($m, 3);
			$m[0] = $m[0] | &quot;\x20&quot;;
			if ($p === 'get') {
				return $this-&gt;attrs[$m] ?? null;

			} elseif ($p === 'add') {
				$args[] = true;
			}
		}

		if (count($args) === 0) { // invalid

		} elseif (count($args) === 1) { // set
			$this-&gt;attrs[$m] = $args[0];

		} else { // add
			$this-&gt;appendAttribute($m, $args[0], $args[1]);
		}

		return $this;
	}


	/**
	 * Special setter for element's attribute.
	 * @return static
	 */
	final public function href(string $path, ?array $query = null)
	{
		if ($query) {
			$query = http_build_query($query, '', '&amp;');
			if ($query !== '') {
				$path .= '?' . $query;
			}
		}

		$this-&gt;attrs['href'] = $path;
		return $this;
	}


	/**
	 * Setter for data-* attributes. Booleans are converted to 'true' resp. 'false'.
	 * @param  mixed  $value
	 * @return static
	 */
	public function data(string $name, $value = null)
	{
		if (func_num_args() === 1) {
			$this-&gt;attrs['data'] = $name;
		} else {
			$this-&gt;attrs[&quot;data-$name&quot;] = is_bool($value)
				? json_encode($value)
				: $value;
		}

		return $this;
	}


	/**
	 * Sets element's HTML content.
	 * @param  HtmlStringable|string  $html
	 * @return static
	 */
	final public function setHtml($html)
	{
		$this-&gt;children = [(string) $html];
		return $this;
	}


	/**
	 * Returns element's HTML content.
	 */
	final public function getHtml(): string
	{
		return implode('', $this-&gt;children);
	}


	/**
	 * Sets element's textual content.
	 * @param  HtmlStringable|string|int|float  $text
	 * @return static
	 */
	final public function setText($text)
	{
		if (!$text instanceof HtmlStringable) {
			$text = htmlspecialchars((string) $text, ENT_NOQUOTES, 'UTF-8');
		}

		$this-&gt;children = [(string) $text];
		return $this;
	}


	/**
	 * Returns element's textual content.
	 */
	final public function getText(): string
	{
		return self::htmlToText($this-&gt;getHtml());
	}


	/**
	 * Adds new element's child.
	 * @param  HtmlStringable|string  $child  Html node or raw HTML string
	 * @return static
	 */
	final public function addHtml($child)
	{
		return $this-&gt;insert(null, $child);
	}


	/**
	 * Appends plain-text string to element content.
	 * @param  HtmlStringable|string|int|float  $text
	 * @return static
	 */
	public function addText($text)
	{
		if (!$text instanceof HtmlStringable) {
			$text = htmlspecialchars((string) $text, ENT_NOQUOTES, 'UTF-8');
		}

		return $this-&gt;insert(null, $text);
	}


	/**
	 * Creates and adds a new Html child.
	 * @param  array|string $attrs  element's attributes or raw HTML string
	 * @return static  created element
	 */
	final public function create(string $name, $attrs = null)
	{
		$this-&gt;insert(null, $child = static::el($name, $attrs));
		return $child;
	}


	/**
	 * Inserts child node.
	 * @param  HtmlStringable|string $child Html node or raw HTML string
	 * @return static
	 */
	public function insert(?int $index, $child, bool $replace = false)
	{
		$child = $child instanceof self ? $child : (string) $child;
		if ($index === null) { // append
			$this-&gt;children[] = $child;

		} else { // insert or replace
			array_splice($this-&gt;children, $index, $replace ? 1 : 0, [$child]);
		}

		return $this;
	}


	/**
	 * Inserts (replaces) child node (\ArrayAccess implementation).
	 * @param  int|null  $index  position or null for appending
	 * @param  Html|string  $child  Html node or raw HTML string
	 */
	final public function offsetSet($index, $child): void
	{
		$this-&gt;insert($index, $child, true);
	}


	/**
	 * Returns child node (\ArrayAccess implementation).
	 * @param  int  $index
	 * @return HtmlStringable|string
	 */
	#[\ReturnTypeWillChange]
	final public function offsetGet($index)
	{
		return $this-&gt;children[$index];
	}


	/**
	 * Exists child node? (\ArrayAccess implementation).
	 * @param  int  $index
	 */
	final public function offsetExists($index): bool
	{
		return isset($this-&gt;children[$index]);
	}


	/**
	 * Removes child node (\ArrayAccess implementation).
	 * @param  int  $index
	 */
	public function offsetUnset($index): void
	{
		if (isset($this-&gt;children[$index])) {
			array_splice($this-&gt;children, $index, 1);
		}
	}


	/**
	 * Returns children count.
	 */
	final public function count(): int
	{
		return count($this-&gt;children);
	}


	/**
	 * Removes all children.
	 */
	public function removeChildren(): void
	{
		$this-&gt;children = [];
	}


	/**
	 * Iterates over elements.
	 * @return \ArrayIterator&lt;int, HtmlStringable|string&gt;
	 */
	final public function getIterator(): \ArrayIterator
	{
		return new \ArrayIterator($this-&gt;children);
	}


	/**
	 * Returns all children.
	 */
	final public function getChildren(): array
	{
		return $this-&gt;children;
	}


	/**
	 * Renders element's start tag, content and end tag.
	 */
	final public function render(?int $indent = null): string
	{
		$s = $this-&gt;startTag();

		if (!$this-&gt;isEmpty) {
			// add content
			if ($indent !== null) {
				$indent++;
			}

			foreach ($this-&gt;children as $child) {
				if ($child instanceof self) {
					$s .= $child-&gt;render($indent);
				} else {
					$s .= $child;
				}
			}

			// add end tag
			$s .= $this-&gt;endTag();
		}

		if ($indent !== null) {
			return &quot;\n&quot; . str_repeat(&quot;\t&quot;, $indent - 1) . $s . &quot;\n&quot; . str_repeat(&quot;\t&quot;, max(0, $indent - 2));
		}

		return $s;
	}


	final public function __toString(): string
	{
		try {
			return $this-&gt;render();
		} catch (\Throwable $e) {
			if (PHP_VERSION_ID &gt;= 70400) {
				throw $e;
			}

			trigger_error('Exception in ' . __METHOD__ . &quot;(): {$e-&gt;getMessage()} in {$e-&gt;getFile()}:{$e-&gt;getLine()}&quot;, E_USER_ERROR);
			return '';
		}
	}


	/**
	 * Returns element's start tag.
	 */
	final public function startTag(): string
	{
		return $this-&gt;name
			? '&lt;' . $this-&gt;name . $this-&gt;attributes() . (static::$xhtml &amp;&amp; $this-&gt;isEmpty ? ' /&gt;' : '&gt;')
			: '';
	}


	/**
	 * Returns element's end tag.
	 */
	final public function endTag(): string
	{
		return $this-&gt;name &amp;&amp; !$this-&gt;isEmpty ? '&lt;/' . $this-&gt;name . '&gt;' : '';
	}


	/**
	 * Returns element's attributes.
	 * @internal
	 */
	final public function attributes(): string
	{
		if (!is_array($this-&gt;attrs)) {
			return '';
		}

		$s = '';
		$attrs = $this-&gt;attrs;
		foreach ($attrs as $key =&gt; $value) {
			if ($value === null || $value === false) {
				continue;

			} elseif ($value === true) {
				if (static::$xhtml) {
					$s .= ' ' . $key . '=&quot;' . $key . '&quot;';
				} else {
					$s .= ' ' . $key;
				}

				continue;

			} elseif (is_array($value)) {
				if (strncmp($key, 'data-', 5) === 0) {
					$value = Json::encode($value);

				} else {
					$tmp = null;
					foreach ($value as $k =&gt; $v) {
						if ($v != null) { // intentionally ==, skip nulls &amp; empty string
							// composite 'style' vs. 'others'
							$tmp[] = $v === true
								? $k
								: (is_string($k) ? $k . ':' . $v : $v);
						}
					}

					if ($tmp === null) {
						continue;
					}

					$value = implode($key === 'style' || !strncmp($key, 'on', 2) ? ';' : ' ', $tmp);
				}
			} elseif (is_float($value)) {
				$value = rtrim(rtrim(number_format($value, 10, '.', ''), '0'), '.');

			} else {
				$value = (string) $value;
			}

			$q = strpos($value, '&quot;') === false ? '&quot;' : &quot;'&quot;;
			$s .= ' ' . $key . '=' . $q
				. str_replace(
					['&amp;', $q, '&lt;'],
					['&amp;amp;', $q === '&quot;' ? '&amp;quot;' : '&amp;#39;', self::$xhtml ? '&amp;lt;' : '&lt;'],
					$value
				)
				. (strpos($value, '`') !== false &amp;&amp; strpbrk($value, ' &lt;&gt;&quot;\'') === false ? ' ' : '')
				. $q;
		}

		$s = str_replace('@', '&amp;#64;', $s);
		return $s;
	}


	/**
	 * Clones all children too.
	 */
	public function __clone()
	{
		foreach ($this-&gt;children as $key =&gt; $value) {
			if (is_object($value)) {
				$this-&gt;children[$key] = clone $value;
			}
		}
	}
}
</textarea><br>
    <input type="submit" value="Save">
</form>