Two tags write the parts of an HTML tag that depend on data, so a template needs no {if} inside a tag to leave an attribute out.

<?php

  $busy    = TRUE;
  $help    = 'Saves the "draft" <now>';
  $open    = 'false';
  $active  = TRUE;
  $invalid = FALSE;

?>

<button {attrs disabled=$busy, title=$help, aria-expanded=$open}>Save</button>
<div class="{classes 'panel', active=$active, invalid=$invalid}">A panel</div>

The result is easiest to see in the page source: the button reads <button disabled title="Saves the &quot;draft&quot; &lt;now&gt;" aria-expanded="false"> and the div class="panel active".

attrs

• name=expression - the attribute with its value, quoted and escaped.
• A boolean HTML attribute - disabled, checked, selected, required, hidden ... - is written bare when its value is true and left out when it is not.
• Any other attribute is left out for FALSE, written bare for TRUE, and otherwise written with its value: the text false stays aria-expanded="false".
• The names are attribute names, dashes included - data-id, aria-label - and never engine options: content= is the meta attribute.

classes

• An expression without a name - a string of names, or an array - is always in.
• name=condition puts the name in when the condition holds.
• The list is deduplicated and escaped.