Easiest way to do a select on table

<?php
/* Get all TemplateVarResource objects where the TV ID is 12 */
$tvrs = $modx->getCollection('modTemplateVarResource', array('templvarid' => '12'));

if (empty($tvrs)) {
    return 'No TVRs found';
}

$output = "";

/* output the resource ID and Value for each one */
foreach ($tvrs as $tvr) {
  $output .= '<br />Resource ID: ' . $tvr->get('contentid');
  $output .= ' ----   Value: ' . $tvr->get('value');
}

return $output;

<?php
/* Get all TemplateVarResource objects where the TV ID is 12 */
$tvrs = $modx->getCollection('modTemplateVarResource', array('templvarid' => '12'));

if (empty($tvrs)) {
    return 'No TVRs found';
}

$output = "";

/* output the resource ID and Value for each one */
foreach ($tvrs as $tvr) {
  $output .= '<br />Resource ID: ' . $tvr->get('contentid');
  $output .= ' ----   Value: ' . $tvr->get('value');
}

return $output;

$c = $modx->newQuery('modTemplateVarResource');
$c->select($modx->getSelectColumns('modTemplateVarResource','','',array('id','contentid','value')));

$c->where(array(
      'tmplvarid' => '25',
));
$collection = $modx->getCollection('modTemplateVarResource', $c);

foreach($collection as $item) {
  $test[] = $item->get('value');
  $test[] = $item->get('contentid');
}

$c->select($modx->getSelectColumns('modTemplateVarResource','','','')));