Problems when running snippet through getResources

<?php
$docId = $modx->getOption('docId', $scriptProperties, '');
  
$tv_param = array(
    'contentid' => $docId, 
    'tmplvarid' => 11 // art_lit id (this is fine)
);

$str = 'TemplateVarResource not found';

{
$i=1;
$tvr = '<citation key="key-[[+tv.art_doi]]-'.$i.'">';
$i++;
}

$tvx = $modx->getObject('modTemplateVarResource', $tv_param);
if ($tvx) { // prevents PHP erors if templateVarResource not found
    $artlit = $tvx->get('value');
    $str = str_replace(array('<li>', '</li>'), array($tvr.'<unstructured_citation>', '</unstructured_citation></citation>'), $artlit);
} else {
    $tv = $modx->getObject('modTemplateVar', 11);
    if ($tv) {
        $str = $tv->get('default_text');
    } else  {
        $str = 'No TV 11';
    }
}

return $str;

<?php
$docId = $modx->getOption('docId', $scriptProperties, '');
$tmplvarids = array(
     1 => 11,
     2 => 12, //change to ID of second TV
);

$str = '';
$i = 1;

foreach($tmplvarids as $tmplvarid) { 

    $prefix = "\n" . '<citation key="key-[[+tv.art_doi]]-'. $i . '"><unstructured_citation>';
    $suffix = '</unstructured_citation></citation>';
    $i++;
    $artlit = '';

    $tvx = $modx->getObject('modTemplateVarResource', array('contentid' => $docId, 'tmplvarid' => $tmplvarid ));

    if ($tvx) { // prevents PHP erors if templateVarResource not found
        $artlit = $tvx->get('value');
    } else {
        $tv = $modx->getObject('modTemplateVar', $tmplvarid);
        if ($tv) {
            $artlit = $tv->get('default_text');
        }
    }
    
    if (empty($artlit)) {
        $artlit = 'Could not get TV value for TV ' . $tmplvarid;
    }

    // $str .= str_replace(array('<li>', '</li>'), array($prefix . '<unstructured_citation>', '</unstructured_citation></citation>'), $artlit);
    // I'm not sure where the li tags are coming from so this seems more straightforward:

    $str .= $prefix . $artlit . $suffix;
}
 
return $str;

<citation key="key--1"><unstructured_citation><ul>
<li>Ayad M. F. Influence of tooth preparation taper and cement type on recementation strength of complete metal crowns / M. F. Ayad, W. M. Johnston, S. F. Rosenstiel // J Prosthet Dent. – 2009. – Vol. 102(6). – P. 354−361.</li>
<li>Begliuk D. A. Functional characterization of the dental pulp and periodontal tissues in patients with partial edentulous / D. A. Begliuk // Res and Educ J. «Health and education in the XXI century». – 2010. – Vol. 12(8). – P. 377–379.</li>
<li>Conrad H. J. Current ceramic materials and systems with clinical recommendations: a systematic review / H. J. Conrad, W. J. Seong, I. J. Pesun // J Prosthet Dent. – 2007. – Vol. 98(5). – P. 389–404.</li>
<li>Davidovich G. The use of CAD/CAM in dentistry / G. Davidovich, P. G. Kotick. // Dent Clin North Am. – 2011. – Vol. 55(3). – P. 559–570.</li>
<li>Etman M. K. Quantitative measurement of tooth and ceramic wear: in vivo study / M. K. Etman, M. Woolford, S. Dunne // Int J Prosthodont. – 2008. – Vol. 21(3). – P. 245−52.</li>
<li>Gasiuk P. A. The influence of orthodontics preparation for the unfixed orthodontic constructions on the tooth pulp from the point of view of morphology / P. A. Gasiuk, V. B. Radchuk, P. P. Brekhlichuk [еt al.] // Intermedical J. – 2015. – Vol. 3(5). – P. 39–43.</li>
<li>Hazhva S. I. Analysis of errors and complications of prosthetics using unremovable prosthetic constructions / S. I. Hazhva, G. A. Pashinian, A. A. Alyoshin // J Dent. – 2010. – Vol. 2. – P. 7–8.</li>
<li>Li R. W. Ceramic dental biomaterials and CAD/CAM technology: State of the art / R. W. Li, T. W. Chow, J. P. Matinlinna // J Prosthodont Res. – 2014. – Vol. 58(4). – P. 208−216.</li>
<li>Mously H. A. Marginal and internal adaptation of ceramic crown restorations fabricated with CAD/CAM technology and the heat-press technique / H. A. Mously, M. Finkelman, R. Zandparsa [еt al.] // J Prosthet Dent. – 2014. – Vol. 112(2). – P. 249−256.</li>
<li>Radchuk V. B. Influence of odontopreparation under the metal-ceramic construction on the tooth tissue / V. B. Radchuk, P. A. Hasiuk, S. O. Rosolovska // Clin Dent. – 2015. – Vol. 3-4(12-13). – P. 129–130.</li>
<li>Reitemeier B. A prospective 10-year study of metal ceramic single crowns and fixed dental prosthesis retainers in private practice set tings / B. Reitemeier, K. Hänsel, C. Kastner [еt al.] // J Prosthet Dent. – 2013. – Vol. 109(3). – P. 149−155.</li>
<li>Іvanitsky І. O. Comparative characteristics of morphometric parameters and histostructure dental hard tissues under conditions of ultrasonic and classical odontoprepations / І. O. Іvanitsky, N. V. Gasyuk, І. Yu. Popovich // Bulletin of the Ukrainian Academy of Medical Dental: Actual problems of modern medicine. – 2013. – Vol. 13(2). – P. 202–205.</li>
</ul></unstructured_citation></citation>
<citation key="key--2"><unstructured_citation>10.26724/2079-8334-2017-3-61-9-11</unstructured_citation></citation>

<citation key="key-10.26724/2079-8334-2017-3-61-9-11-1"><unstructured_citation>Ayad M. F. Influence of tooth preparation taper and cement type on recementation strength of complete metal crowns / M. F. Ayad, W. M. Johnston, S. F. Rosenstiel // J Prosthet Dent. – 2009. – Vol. 102(6). – P. 354−361.</unstructured_citation></citation>
<citation key="key-10.26724/2079-8334-2017-3-61-9-11-2"><unstructured_citation>Begliuk D. A. Functional characterization of the dental pulp and periodontal tissues in patients with partial edentulous / D. A. Begliuk // Res and Educ J. «Health and education in the XXI century». – 2010. – Vol. 12(8). – P. 377–379.</unstructured_citation></citation>

[[+tv.art_doi]]

$docId = $modx->getOption('docId', $scriptProperties, '');
$tmplvarids = array(
     1 => 11,
     2 => 17, 
);

$str = '';
$i = 1;
 
foreach($tmplvarids as $tmplvarid) { 

    $prefix = "\n" . '<citation key="key-[[+tv.art_doi]]-'. $i . '">';
    $suffix = '';
    $i++;
    $artlit = '';
 
    $tvx = $modx->getObject('modTemplateVarResource', array('contentid' => $docId, 'tmplvarid' => $tmplvarid ));
 
    if ($tvx) { // prevents PHP erors if templateVarResource not found
        $artlit = $tvx->get('value');
    } else {
        $tv = $modx->getObject('modTemplateVar', $tmplvarid);
        if ($tv) {
            $artlit = $tv->get('default_text');
        }
    }
     
    if (empty($artlit)) {
        $artlit = 'Could not get TV value for TV ' . $tmplvarid;
    }

    $str .= str_replace(array('<li>', '</li>'), array($prefix . '<unstructured_citation>', '</unstructured_citation></citation>'), $artlit);

}

return $str;

<ul>

<citation key="key--1"><unstructured_citation>Ayad M. F. Influence of tooth preparation taper and cement type on recementation strength of complete metal crowns / M. F. Ayad, W. M. Johnston, S. F. Rosenstiel // J Prosthet Dent. – 2009. – Vol. 102(6). – P. 354−361.</unstructured_citation></citation>

<citation key="key--1"><unstructured_citation>Begliuk D. A. Functional characterization of the dental pulp and periodontal tissues in patients with partial edentulous / D. A. Begliuk // Res and Educ J. «Health and education in the XXI century». – 2010. – Vol. 12(8). – P. 377–379.</unstructured_citation></citation>

<citation key="key--1"><unstructured_citation>Conrad H. J. Current ceramic materials and systems with clinical recommendations: a systematic review / H. J. Conrad, W. J. Seong, I. J. Pesun // J Prosthet Dent. – 2007. – Vol. 98(5). – P. 389–404.</unstructured_citation></citation>

<citation key="key--1"><unstructured_citation>Davidovich G. The use of CAD/CAM in dentistry / G. Davidovich, P. G. Kotick. // Dent Clin North Am. – 2011. – Vol. 55(3). – P. 559–570.</unstructured_citation></citation>

<citation key="key--1"><unstructured_citation>Etman M. K. Quantitative measurement of tooth and ceramic wear: in vivo study / M. K. Etman, M. Woolford, S. Dunne // Int J Prosthodont. – 2008. – Vol. 21(3). – P. 245−52.</unstructured_citation></citation>

<citation key="key--1"><unstructured_citation>Gasiuk P. A. The influence of orthodontics preparation for the unfixed orthodontic constructions on the tooth pulp from the point of view of morphology / P. A. Gasiuk, V. B. Radchuk, P. P. Brekhlichuk [еt al.] // Intermedical J. – 2015. – Vol. 3(5). – P. 39–43.</unstructured_citation></citation>

<citation key="key--1"><unstructured_citation>Hazhva S. I. Analysis of errors and complications of prosthetics using unremovable prosthetic constructions / S. I. Hazhva, G. A. Pashinian, A. A. Alyoshin // J Dent. – 2010. – Vol. 2. – P. 7–8.</unstructured_citation></citation>

<citation key="key--1"><unstructured_citation>Li R. W. Ceramic dental biomaterials and CAD/CAM technology: State of the art / R. W. Li, T. W. Chow, J. P. Matinlinna // J Prosthodont Res. – 2014. – Vol. 58(4). – P. 208−216.</unstructured_citation></citation>

<citation key="key--1"><unstructured_citation>Mously H. A. Marginal and internal adaptation of ceramic crown restorations fabricated with CAD/CAM technology and the heat-press technique / H. A. Mously, M. Finkelman, R. Zandparsa [еt al.] // J Prosthet Dent. – 2014. – Vol. 112(2). – P. 249−256.</unstructured_citation></citation>

<citation key="key--1"><unstructured_citation>Radchuk V. B. Influence of odontopreparation under the metal-ceramic construction on the tooth tissue / V. B. Radchuk, P. A. Hasiuk, S. O. Rosolovska // Clin Dent. – 2015. – Vol. 3-4(12-13). – P. 129–130.</unstructured_citation></citation>

<citation key="key--1"><unstructured_citation>Reitemeier B. A prospective 10-year study of metal ceramic single crowns and fixed dental prosthesis retainers in private practice set tings / B. Reitemeier, K. Hänsel, C. Kastner [еt al.] // J Prosthet Dent. – 2013. – Vol. 109(3). – P. 149−155.</unstructured_citation></citation>

<citation key="key--1"><unstructured_citation>Іvanitsky І. O. Comparative characteristics of morphometric parameters and histostructure dental hard tissues under conditions of ultrasonic and classical odontoprepations / І. O. Іvanitsky, N. V. Gasyuk, І. Yu. Popovich // Bulletin of the Ukrainian Academy of Medical Dental: Actual problems of modern medicine. – 2013. – Vol. 13(2). – P. 202–205.</unstructured_citation></citation>
</ul>10.26724/2079-8334-2017-3-61-9-11