Void elements do not contain values or closing tags.
See also
http://www.w3.org/TR/html5/syntax.html#syntax-start-tag
http://www.w3.org/TR/html5/syntax.html#void-elements
File
core/lib/Drupal/Core/Render/Element/HtmlTag.php, line 41
Class
HtmlTag Provides a render element for any HTML tag, with properties and value.
Namespace
Drupal\Core\Render\Element
Code
static protected $voidElements = array(
'area', 'base', 'br', 'col', 'embed', 'hr', 'img', 'input',
'keygen', 'link', 'meta',