printPlaceholders snippet

printPlaceholders.php

<?php 
if (!$modx->user->isAuthenticated('mgr')) return;

$placeholders = $prefix ? array() : $modx->placeholders;

if ($prefix) {
    foreach ($modx->placeholders as $key => $ph) {
        if (strpos($key, $prefix) === 0) {
            $placeholders[$key] = $ph;
        }
    }
}    
return '<pre>' . print_r($placeholders, true) . '</pre>';