The Markup class is used to strip HTML tags and replace BBcode with HTML. It can also be used to format code so the tags can be displayed correctly.
print Markup::replaceTags('[b]This is bold![/b]');
print Markup::replaceTags('[u]This is underlined![/u]');
print Markup::replaceTags('[i]This is italic![/i]');
print Markup::replaceTags('[url=http://www.example.org]This is a link![/url]');
print Markup::replaceTags('[img]http://www.example.org/image.gif[/img]');
print Markup::replaceTags('[tab]');
print Markup::replaceTags('[url=http://www.example.org" onclick="javascript:alert(1);"]This will intentionally break![/url]');
print Markup::formatCode('
<p>This is <?php echo($strAdjective); ?>!</p>
');