protected static function 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. Null args[] values are deprecated in Drupal 9.5 and will fail in Drupal 11.0. 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.

See also

\Drupal\Core\StringTranslation\TranslatableMarkup

\Drupal\Core\StringTranslation\PluralTranslatableMarkup

\Drupal\Component\Utility\Html::escape()

\Drupal\Component\Utility\UrlHelper::stripDangerousProtocols()

\Drupal\Core\Url::fromUri()

File

core/lib/Drupal/Component/Render/FormattableMarkup.php, line 196

Class

FormattableMarkup

Formats a string for HTML display by replacing variable placeholders.

Namespace

Code

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

  // Transform arguments before inserting them.
  foreach ($args as $key => $value) {
    if (is_null($value)) {

      // It's probably a bug to provide a null value for the placeholder arg,
      // and in D11 this will no longer be allowed. When this trigger_error
      // is removed, also remove isset $value checks inside the switch{}
      // below.
      // phpcs:ignore Drupal.Semantics.FunctionTriggerError
      @trigger_error(sprintf('Deprecated NULL placeholder value for key (%s) in: "%s". This will throw a PHP error in drupal:11.0.0. See https://www.drupal.org/node/3318826', (string) $key, (string) $string), E_USER_DEPRECATED);
      $value = '';
    }
    switch ($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.
        // Strings that are safe within HTML fragments, but not within other
        // contexts, may still be an instance of
        // \Drupal\Component\Render\MarkupInterface, 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 whether the value is an
        // instance of \Drupal\Component\Render\MarkupInterface. 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\Render\MarkupInterface and also due to the
        // wrapping markup.
        $args[$key] = '<em class="placeholder">' . static::placeholderEscape($value) . '</em>';
        break;
      default:
        if (!ctype_alnum($key[0])) {

          // Warn for random placeholders that won't be replaced.
          trigger_error(sprintf('Placeholders must begin with one of the following "@", ":" or "%%", invalid placeholder (%s) with string: "%s"', $key, $string), E_USER_WARNING);
        }

        // No replacement possible therefore we can discard the argument.
        unset($args[$key]);
        break;
    }
  }
  return strtr($string, $args);
}