display "related" results with tags?

<?php
/*
--------------------------------------------------
randomTag
[[randomTag? &docid=`` &tvtag=`` &delimiter=``]]
--------------------------------------------------
Parameters
--------------------------------------------------
*/

# $docid [ int ]
# ID of the document for which to get a template variable content.
# Default: current document

$rtIntDocId = (isset($docId)) ? $docid : $modx->documentIdentifier;

# $tvtag [ string ]
# Name of the field where the tags are located.
# Default: 'null'

$rtStrDocField = (isset($tvtag)) ? trim($tvtag) : 'null';

# $delimiter [ string ]
# The delimiter that seporates the tags in the template variable.
# Default: ", "

$rtBoolDelimiter = (isset($delimiter)) ? $delimiter : ', ';

/* Do not edit the code below!
----------------------------------------------- */
# get content of the field
$output = $modx->getTemplateVarOutput($rtStrDocField,$rtIntDocId);
$field = $output[$rtStrDocField];

# break out tags from field
$rtSplit = split($rtBoolDelimiter, $field);

# count number of tags
$rtSplitNumber = count($rtSplit);

# select random number and associate array
$rtNum = rand(1, $rtSplitNumber);
$rtNum = $rtNum - 1;

# clear it
unset($rtIntDocId, $rtStrDocField, $rtBoolDelimiter);

return $rtSplit[$rtNum];
?>

[!Ditto? &filter=`tvpage_tags,[[randomTag]],2` &display=`3` &tpl=`ditto_related_items` !]

[!Ditto? &filter=`[[randomTag? &tvtag=`vpage_tags`]],2` &display=`3` &tpl=`ditto_related_items` !]