getResourceThumbnails snippet for MODX. Searches inside the tv_posttype field and pulls out the images for use in open graph tags. If the resource is a "default" resource, it will display the default Open Graph image from ClientConfig.

getResourceThumbnails.snippet.php

<?php
/**
 * getResourceThumbnails snippet
 * Searches inside the tv_posttype field, and pulls out images
 * for use in Open Graph tags.
 * If the resource is a default resource, it displays the default
 * Open Graph image from ClientConfig
 * 
 *
 * @author Jon Leverrier (jon@youandmedigital.com)
 * @version 1.0
 * @since 10th December 2017
 */
 
 
// get current page ID
$id = (!empty($id) ? $id : $modx->resource->get('id'));
$resId = (!empty($id) ? $id : $modx->resource->get('id'));

// fetch some system settings to use to make the url
$baseUrl = $modx->getOption('http_host');
$server = $modx->getOption('server_protocol');

// get baseUrl path for media source with ID 2
$mediaSource = $modx->getObject('modMediaSource', 2);
$properties = $mediaSource->getProperties();
$mediaSourcePath = $properties['baseUrl']['value'];

// name of tv to inspect
$tvName = tv_posttype;

// post type template vars
$tvThumbBlog = tv_pt_blog_thumbnail;
$tvThumbNews = tv_pt_news_thumbnail;
$tvThumbEvent = tv_pt_event_thumbnail;
$tvThumbProject = tv_pt_project_thumbnail;
$tvThumbProperty = tv_pt_property_thumbnail;
$tvThumbService = tv_pt_service_thumbnail;
$tvThumbTeam = tv_pt_team_profilepicture;
$tvThumbResource = tv_pt_resource_thumbnail;

// imageplus chunk template to use for output
$imagePlusTpl = tpl_head_thumbnail;
$imagePlusTplPerson = tpl_head_thumbnail_person;


// get default open graph image from client config
$outputDeafultImg = array();
$getClientConfigImg = $modx->query("SELECT * FROM `modx_clientconfig_setting` WHERE `id` ='4'");
if ($getClientConfigImg) {
    while ($row = $getClientConfigImg->fetch(PDO::FETCH_ASSOC)) {
        $placeholders = array_merge($scriptProperties, $row);
        $outputDeafultImg[] = print_r($placeholders[value], true);
    }
}
$getClientConfigImageClean = @implode("\n", $outputDeafultImg);
$getClientConfigImageUrl = $server . '://' . $baseUrl . $mediaSourcePath . $getClientConfigImageClean;

// get tv label per $resId for the tv defined in $tvName
$resources = array();
if ($resId) {
    $resId = @explode(',', $resId);
    $resources = $modx->getCollection('modResource', array(
        'id:IN' => $resId
    ));
}
if (empty($resources)) {
    $modx->log(modX::LOG_LEVEL_ERROR, '[getResourceThumbnails] : $resources is empty');
    return;
}
$tv = $modx->getObject('modTemplateVar', array(
    'name' => $tvName
        ));
if (empty($tv)) {
    return;
}
$outputArray = array();
foreach ($resources as $resource) {
    $tvValue = $resource->getTVValue($tvName);
    $inputOptions = $tv->parseInputOptions($tv->processBindings($tv->get('elements'), $resource->get('id')));
    $tvOptions = array();
    foreach ($inputOptions as $v) {
        $exp = @explode('==', $v);
        $text = isset($exp[1]) ? $exp[0] : $exp[0];
        $val = isset($exp[1]) ? $exp[1] : $exp[0];
        $tvOptions[$val] = $text;
    }
    $values = array_map('trim', @explode('||', $tvValue));
    foreach ($values as $value) {
        if (empty($value)) {
            continue;
        }
        if (isset($outputArray[$value])) {
            continue;
        }
        else {
            $outputArray[$value] = $tvOptions[$value];
        }
    }
}

$myTvLabel = @implode('\n', $outputArray);

// if tv is set to default "please select", do something...
if (strpos($myTvLabel, 'Please select...') !== false) {
    
    // check to see if the tv value is empty
    if (empty($getClientConfigImageClean)) {
        return;
    }
    else {
        return $getClientConfigImageUrl;
    }

}
// if tv is set to default "News", do something...
if (strpos($myTvLabel, 'News') !== false) {
    
    $outputCachedImage = $modx->runSnippet('ImagePlus', array(
        'tvname' => $tvThumbNews,
        'docid' => $id,
        'type' => 'tpl',
        'tpl' => $imagePlusTpl
         
    ));
    
    $finalOutput = $server . '://' . $baseUrl . $outputCachedImage;
    
    // check to see if the tv value is empty
    if (empty($outputCachedImage)) {
        return;
    }
    else {
        return $finalOutput;
    }
 
}
// if tv is set to default "Blog", do something...
if (strpos($myTvLabel, 'Blog') !== false) {
    
    $outputCachedImage = $modx->runSnippet('ImagePlus', array(
        'tvname' => $tvThumbBlog,
        'docid' => $id,
        'type' => 'tpl',
        'tpl' => $imagePlusTpl
         
    ));
    
    $finalOutput = $server . '://' . $baseUrl . $outputCachedImage;
    
    // check to see if the tv value is empty
    if (empty($outputCachedImage)) {
        return;
    }
    else {
        return $finalOutput;
    }
 
}
// if tv is set to default "Event", do something...
if (strpos($myTvLabel, 'Event') !== false) {
    
    $outputCachedImage = $modx->runSnippet('ImagePlus', array(
        'tvname' => $tvThumbEvent,
        'docid' => $id,
        'type' => 'tpl',
        'tpl' => $imagePlusTpl
         
    ));
    
    $finalOutput = $server . '://' . $baseUrl . $outputCachedImage;
    
    // check to see if the tv value is empty
    if (empty($outputCachedImage)) {
        return;
    }
    else {
        return $finalOutput;
    }
 
}
// if tv is set to default "Project", do something...
if (strpos($myTvLabel, 'Project') !== false) {
    
    $outputCachedImage = $modx->runSnippet('ImagePlus', array(
        'tvname' => $tvThumbProject,
        'docid' => $id,
        'type' => 'tpl',
        'tpl' => $imagePlusTpl
         
    ));
    
    $finalOutput = $server . '://' . $baseUrl . $outputCachedImage;
    
    // check to see if the tv value is empty
    if (empty($outputCachedImage)) {
        return;
    }
    else {
        return $finalOutput;
    }
 
}
// if tv is set to default "Property", do something...
if (strpos($myTvLabel, 'Property') !== false) {
    
    $outputCachedImage = $modx->runSnippet('ImagePlus', array(
        'tvname' => $tvThumbProperty,
        'docid' => $id,
        'type' => 'tpl',
        'tpl' => $imagePlusTpl
         
    ));
    
    $finalOutput = $server . '://' . $baseUrl . $outputCachedImage;
    
    // check to see if the tv value is empty
    if (empty($outputCachedImage)) {
        return;
    }
    else {
        return $finalOutput;
    }
 
}
// if tv is set to default "Service", do something...
if (strpos($myTvLabel, 'Service') !== false) {
    
    $outputCachedImage = $modx->runSnippet('ImagePlus', array(
        'tvname' => $tvThumbService,
        'docid' => $id,
        'type' => 'tpl',
        'tpl' => $imagePlusTpl
         
    ));
    
    $finalOutput = $server . '://' . $baseUrl . $outputCachedImage;
    
    // check to see if the tv value is empty
    if (empty($outputCachedImage)) {
        return;
    }
    else {
        return $finalOutput;
    }
 
}
// if tv is set to default "Person", do something...
if (strpos($myTvLabel, 'Person') !== false) {
    
    $outputCachedImage = $modx->runSnippet('ImagePlus', array(
        'tvname' => $tvThumbTeam,
        'docid' => $id,
        'type' => 'tpl',
        'tpl' => $imagePlusTplPerson
         
    ));
    
    $finalOutput = $server . '://' . $baseUrl . $outputCachedImage;
    
    // check to see if the tv value is empty
    if (empty($outputCachedImage)) {
        return;
    }
    else {
        return $finalOutput;
    }
 
}
// if tv is set to default "Resource", do something...
if (strpos($myTvLabel, 'Resource') !== false) {
    
    $outputCachedImage = $modx->runSnippet('ImagePlus', array(
        'tvname' => $tvThumbResource,
        'docid' => $id,
        'type' => 'tpl',
        'tpl' => $imagePlusTpl
         
    ));
    
    $finalOutput = $server . '://' . $baseUrl . $outputCachedImage;
    
    // check to see if the tv value is empty
    if (empty($outputCachedImage)) {
        return;
    }
    else {
        return $finalOutput;
    }
 
}