emulate @Directory binding, but from base_path of Resource's context #MODX

context_directory_binding.php

<?php
/**
 * emulate @DIRECTORY binding, from base_path of Resource's context
 *
 * usage:
 * a) create context settings named 'base_path' for each context (not neccessary for web context)
 *    (note: you may also want assets_path and/or other settings in your contexts as well)
 * b) call with @EVAL in TV's Input Options field, e.g.
 * @EVAL $dir='assets/images/'; return(include '/path/to/this/file/context_directory_binding.php');
 */
$dirBasePath = $this->xpdo->getOption('base_path');
$actionController = 'resource/create';
$actionId = $modx->request->action;
if(is_numeric($actionId) && isset($modx->actionMap[$actionId])) {
    $actionController = $modx->actionMap[$actionId]['controller'];
}

// get context
$contextKey = '';
if($actionController == 'resource/update') {
    $resourceId = (int) $_REQUEST['id'];
    $contextQuery = $modx->newQuery('modResource', $resourceId, false);
    $contextQuery->select($modx->getSelectColumns('modResource', 'modResource', '', array('context_key')));
    $contextQuery->prepare();
    $contextQuery->stmt->execute();
    $contextKey = $contextQuery->stmt->fetchColumn();
} else {
    if(isset($_REQUEST['context_key'])) {
        $contextKey = $_REQUEST['context_key'];
    }
}
if(empty($contextKey)) {
    $contextKey = 'web';
}

// get base path
$basePathSetting = $modx->getObject('modContextSetting', array(
    'context_key'=> $contextKey,
    'key'=> 'base_path'
));
$basePath = $modx->getOption('base_path');
if($basePathSetting !== null) {
    $basePath = $basePathSetting->get('value');
}

// make sure specified folder exists ($dir passed from @EVAL
if (substr($basePath,-1,1) != '/') { $basePath .= '/'; }
if (substr($dir,-1,1) != '/') { $dir .= '/'; }
$targetPath = $basePath . str_replace('..', '.', $dir);

// do @DIRECTORY logic
if (!is_dir($targetPath)) { return ''; }
$files = array();
$invalid = array('.','..','.svn','.git','.DS_Store');
foreach (new DirectoryIterator($targetPath) as $file) {
    if (!$file->isReadable()) continue;
    $basename = $file->getFilename();
    if(!in_array($basename,$invalid)) {
        $files[] = "{$basename}=={$param}{$basename}";
    }
}
asort($files);
$output = implode('||',$files);

return $output;