protected static function FormattableMarkup::placeholderFormat in Zircon Profile 8.0

Same name and namespace in other branches

8 core/lib/Drupal/Component/Render/FormattableMarkup.php \Drupal\Component\Render\FormattableMarkup::placeholderFormat()

Replaces placeholders in a string with values.

Parameters

string $string: A string containing placeholders. The string itself is expected to be safe and correct HTML. Any unsafe content must be in $args and inserted via placeholders.

array $args: An associative array of replacements. Each array key should be the same as a placeholder in $string. The corresponding value should be a string or an object that implements \Drupal\Component\Render\MarkupInterface. The value replaces the placeholder in $string. Sanitization and formatting will be done before replacement. The type of sanitization and formatting depends on the first character of the key:

@variable: When the placeholder replacement value is:
- A string, the replaced value in the returned string will be sanitized using \Drupal\Component\Utility\Html::escape().
- A MarkupInterface object, the replaced value in the returned string will not be sanitized.
- A MarkupInterface object cast to a string, the replaced value in the returned string be forcibly sanitized using \Drupal\Component\Utility\Html::escape().


        $this->placeholderFormat('This will force HTML-escaping of the replacement value: @text', ['@text' => (string) $safe_string_interface_object));

Use this placeholder as the default choice for anything displayed on the site, but not within HTML attributes, JavaScript, or CSS. Doing so is a security risk.

%variable: Use when the replacement value is to be wrapped in <em> tags. A call like:

$string = "%output_text";
$arguments = [
  'output_text' => 'text output here.',
];
$this
  ->placeholderFormat($string, $arguments);

makes the following HTML code:


      <em class="placeholder">text output here.</em>

As with @variable, do not use this within HTML attributes, JavaScript, or CSS. Doing so is a security risk.

:variable: Return value is escaped with \Drupal\Component\Utility\Html::escape() and filtered for dangerous protocols using UrlHelper::stripDangerousProtocols(). Use this when using the "href" attribute, ensuring the attribute value is always wrapped in quotes:

// Secure (with quotes):
$this
  ->placeholderFormat('<a href=":url">@variable</a>', [
  ':url' => $url,
  @variable => $variable,
]);

// Insecure (without quotes):
$this
  ->placeholderFormat('<a href=:url>@variable</a>', [
  ':url' => $url,
  @variable => $variable,
]);

When ":variable" comes from arbitrary user input, the result is secure, but not guaranteed to be a valid URL (which means the resulting output could fail HTML validation). To guarantee a valid URL, use Url::fromUri($user_input)->toString() (which either throws an exception or returns a well-formed URL) before passing the result into a ":variable" placeholder.

Return value

string A formatted HTML string with the placeholders replaced.

File

core/lib/Drupal/Component/Render/FormattableMarkup.php, line 194: Contains \Drupal\Component\Render\FormattableMarkup.

Class

FormattableMarkup: Formats a string for HTML display by replacing variable placeholders.

Namespace

Drupal\Component\Render

Code

protected static function placeholderFormat($string, array $args) {

  // Transform arguments before inserting them.
  foreach ($args as $key => $value) {
    switch ($key[0]) {
      case '@':

        // Escape if the value is not an object from a class that implements
        // \Drupal\Component\Render\MarkupInterface, for example strings will
        // be escaped.
        // \Drupal\Component\Utility\SafeMarkup\SafeMarkup::isSafe() may
        // return TRUE for content that is safe within HTML fragments, but not
        // within other contexts, so this placeholder type must not be used
        // within HTML attributes, JavaScript, or CSS.
        $args[$key] = static::placeholderEscape($value);
        break;
      case ':':

        // Strip URL protocols that can be XSS vectors.
        $value = UrlHelper::stripDangerousProtocols($value);

        // Escape unconditionally, without checking
        // \Drupal\Component\Utility\SafeMarkup\SafeMarkup::isSafe(). This
        // forces characters that are unsafe for use in an "href" HTML
        // attribute to be encoded. If a caller wants to pass a value that is
        // extracted from HTML and therefore is already HTML encoded, it must
        // invoke
        // \Drupal\Component\Render\OutputStrategyInterface::renderFromHtml()
        // on it prior to passing it in as a placeholder value of this type.
        // @todo Add some advice and stronger warnings.
        //   https://www.drupal.org/node/2569041.
        $args[$key] = Html::escape($value);
        break;
      case '%':

        // Similarly to @, escape non-safe values. Also, add wrapping markup
        // in order to render as a placeholder. Not for use within attributes,
        // per the warning above about
        // \Drupal\Component\Utility\SafeMarkup\SafeMarkup::isSafe() and also
        // due to the wrapping markup.
        $args[$key] = '<em class="placeholder">' . static::placeholderEscape($value) . '</em>';
        break;
      default:

        // We do not trigger an error for placeholder that start with an
        // alphabetic character.
        if (!ctype_alpha($key[0])) {

          // We trigger an error as we may want to introduce new placeholders
          // in the future without breaking backward compatibility.
          trigger_error('Invalid placeholder: ' . $key, E_USER_ERROR);
        }
        break;
    }
  }
  return strtr($string, $args);
}

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