Kirby icon tag with svg sprites

icon.php

<?php

kirbytext::$tags['icon'] = array(
  'attr' => array(
    'rel',
    'link',
    'target',
    'width',
    'height',
    'class',
    'color',
    'align'
  ),
  'html' => function($tag) {

    $icon = $tag->attr('icon');

    $width = $tag->attr('width');
    $height = $tag->attr('height');
    if ($width == '') {
      $width = '36';
    }
    if ($height == '') {
      //icons are square by default
      $height = $width;
    }

    $iconColor = '';
    if ($tag->attr('color')) {
      $iconColor = '-'.$tag->attr('color');
    }
    $iconUrl = url('assets/icons/'.$icon.$iconColor.'.svg');

    $iconAttrs = attr(array(
      //'src' => $iconUrl,
      'title' => $tag->attr('icon'),
      'width' => $width,
      'height' => $height,
      'class' => 'icon ' . $tag->attr('class') .' '. $tag->attr('color').'-bg'
    ));

    // $iconElement = '<img '.$iconAttrs.' role="presentation">';

    $iconElement = '<svg '.$iconAttrs.' viewBox="0 0 '.$width.' '.$height.'">';
    $iconElement .= '<use xlink:href="'.url('assets/sprites/icons.svg#').$icon.'"></use>';
    $iconElement .= '</svg>';

    if ($tag->attr('link') != '') {
      $linkAttrs = attr(array(
        'rel' => $tag->attr('rel'),
        'href' => $tag->attr('link'),
        'target' => $tag->attr('target'),
        'class' => 'icon-link'
      ));
      return '<a '.$linkAttrs.'>'.$iconElement.'</a>';
    } else {
      return $iconElement;
    }

  }
);

?>