I'm seeing numerous errors in our server log like this:

NOTICE: Use of undefined constant String - assumed 'String' (/var/www/html/ojs/plugins/citationFormats/abnt/AbntCitationPlugin.inc.php:98)

I've located the problematic function:

	function displayCitation(&$article, &$issue, &$journal) {
		$templateMgr =& TemplateManager::getManager();
		$templateMgr->register_modifier('mb_upper', array(String, 'strtoupper'));
		return parent::displayCitation($article, $issue, $journal);
	}

The register_modifier('mb_upper', array(String, 'strtoupper')); function apparently uses undefined constant String. Could it be that it should be just put in quotes? I just did that, and it seems that the errors have stopped, but I don't know if the function now works as it should...

I'm using OJS 2.4.0.