function image_add_svg_attributes

Add attributes to an SVG string.

@since 1.28.0 Function added.

Parameters

string $svg_content: The entire contents of an SVG image.

array $attributes: An array of attributes to add to the SVG image. The special case of an "alt" attribute is automatically converted to a child <title> element, which is the accessible mechanism for alternative text within SVGs.

Return value

string: The SVG image contents with the attributes added. An empty string in case of errors.

Related topics

File

core/includes/image.inc, line 585

API for manipulating images.

Code

function image_add_svg_attributes($svg_content, array $attributes) {
  $doc = new DOMDocument();
  libxml_use_internal_errors(TRUE);
  $doc->loadXML($svg_content);
  $svg_tag = $doc->getElementsByTagName('svg')->item(0);
  $last_error = libxml_get_last_error();
  libxml_use_internal_errors(FALSE);
  if (empty($svg_tag)) {
    $message = $last_error ? trim($last_error->message) : '';
    watchdog('image', 'Failed to parse SVG content. %message', array(
      '%message' => $message,
    ), WATCHDOG_ERROR);
    return '';
  }

  // Convert the alt attribute to a <title> element.
  if (isset($attributes['alt'])) {
    if (strlen($attributes['alt'])) {
      $title = $doc->createElement('title');
      $title->textContent = $attributes['alt'];
      // Since DOMDocument::prepend() is not available in PHP versions prior
      // to v8, we are using DOMNode::insertBefore().
      $svg_tag->insertBefore($title, $svg_tag->firstChild);
    }
    // Remove any given <title> element if alt is an empty string.
    elseif ($svg_tag->firstChild && $svg_tag->firstChild->nodeName === 'title') {
      $svg_tag->removeChild($svg_tag->firstChild);
    }
    unset($attributes['alt']);
  }

  foreach ($attributes as $attribute_name => $attribute_value) {
    $attribute_value = implode(' ', (array) $attribute_value);
    if (strlen($attribute_value)) {
      $svg_tag->setAttribute($attribute_name, $attribute_value);
    }
    else {
      $svg_tag->removeAttribute($attribute_name);
    }
  }
  return $doc->saveXML($svg_tag);
}