Quick snippet to set placeholders from a JSON array. Made basically so I could create MIGXs inside MIGXS. There is little error checking are anything else at this point. Use at your own risk.

modx-json-to-placeholders

<?php
/**
 * jsonToPlaceholders snippet for JM Customer Database extra
 *
 * Copyright 2013 by JM Addington jm@jmaddington.com
 * Created on 04-28-2013
 *
 * @package jmc
 */

/**
 * Description
 * -----------
 * Sets a JSON array to placeholders
 *
 * Variables
 * ---------
 * @var $modx modX
 * @var $scriptProperties array
 * @var $json string   JSON Array to parse
 * @var $tpl   string,optional         Name of chunk to use a template
 * @var $code  string,optional         Use as template instead of chunk
 * @var $ph    string,optional          Placeholder to set instead of simply returning parsed content
 * @var $skipFirstLevel    boolean,optional If set to true, skips the first level of the array. Basically for MIGX support
 * @var $loop  boolean,optional          If set to true, loops through the first array level and parses
 * @var $idxPrefix  boolean,optional          If set prefixes the idx placeholder with the given value
 * @var $debug  boolean,optional         If set to true dump $scriptProperties
 *
 * @package jmc
 **/

$json = $modx->getOption('json', $scriptProperties);
$chunkName = $modx->getOption('tpl', $scriptProperties);
$code = $modx->getOption('code', $scriptProperties);
$ph = $modx->getOption('ph', $scriptProperties);
$loop = $modx->getOption('loop', $scriptProperties, false);
$skipFirstLevel = $modx->getOption('skipFirstLevel', $scriptProperties, false);
$debug = $modx->getOption('debug', $scriptProperties, false);
$idxPrefix = $modx->getOption('idxPrefix', $scriptProperties, '');

$output = '';

$phpArray = $modx->fromJSON($json);

$phpArray = $skipFirstLevel? $phpArray[0] : $phpArray;
$idx = 1;
//If we aren't looping, just process the array like normal, setting placeholders directly.
if (!$loop) {
    if ($code != "") {

        //Create a temporary chunk for the code
        $uniqid = uniqid();
        $c = $modx->newObject('modChunk', array('name' => "{tmp}-{$uniqid}"));
        $c->setCacheable(false);

        $output  = $c->process($phpArray, $code);
    } else {
        if ($chunkName != "") {
            $output = $modx->getChunk($chunkName, $phpArray);
        }
    }
} else {
    //If we are looping, well, loop!
    if ($code != "") {

        //Create a temporary chunk for the code
        $uniqid = uniqid();
        $c = $modx->newObject('modChunk', array('name' => "{tmp}-{$uniqid}"));
        $c->setCacheable(false);

        foreach ($phpArray as $row) {
            $output  .= $c->process($phpArray, $row);
        }
    } else {
        if ($chunkName != "") {
            foreach ($phpArray as $row) {
                $row = array_merge($row, array('idx' => $idx));
                $row = array_merge($row, array("$idxPrefix" => $row["idx"]));
                $output .= $modx->getChunk($chunkName, $row);
                $idx++;
            }
        }
    }
}

if ($debug){
    $output .= 'ScriptProperties: ' . print_r($scriptProperties, true);
    $output .= 'phpArray: ' .print_r($phpArray, true);
}

if ($chunkName == "" && $code == "") {
    $output .= print_r($phpArray, true);
}

if ($ph != "") {
    $modx->setPlaceholder($ph, $output);
} else {
    return $output;
}