Issue with Schema and custom fields

Hi, I have the next code in footer.php

?>
<?php if(get_post_meta(get_the_id(), 'es_una_receta', true)) { ?>
<script type="application/ld+json">
 {
 "@context": "http://schema.org/",
 "@type": "Recipe",
 "name": "<?php echo get_post_meta(get_the_id(), 'nombre_receta', true); ?>",
 "image": "<?php echo get_post_meta(get_the_id(), 'imagen_receta', true); ?>",
 "author": {
 "@type": "Person",
 "name": "<?php echo get_post_meta(get_the_id(), 'autor_receta', true); ?>"
 },
 "datePublished": "<?php the_date() ?>",
 "description": "<?php echo get_post_meta(get_the_id(), 'descripcion_receta', true); ?>",
 "prepTime": "<?php echo get_post_meta(get_the_id(), 'tiempo_prep_receta', true); ?>",
 "cooktime": "<?php echo get_post_meta(get_the_id(), 'tiempo_coccion_receta', true); ?>",
 "totalTime": "<?php echo get_post_meta(get_the_id(), 'tiempo_total_receta', true); ?>",
 "keywords": "<?php echo get_post_meta(get_the_id(), 'keywords_receta', true); ?>",
 "recipeYield": "<?php echo get_post_meta(get_the_id(), 'comensal_receta', true); ?>",
 "recipecategory": "<?php echo get_post_meta(get_the_id(), 'categoria_receta', true); ?>",
 "recipeIngredient": <?php echo json_encode(explode(",", get_post_meta(get_the_id(), 'ingredientes_recetas', true))); ?>,
 "recipeInstructions": "<?php echo get_post_meta(get_the_id(), 'instrucciones_receta', true); ?>",
 "aggregateRating": {
 "@type": "AggregateRating",
 "ratingValue": "<?php echo get_post_meta(get_the_id(), 'rating_average', true); ?>",
 "ratingCount": "<?php echo get_post_meta(get_the_id(), 'rating_count', true); ?>"
 },
}
</script>
<?php } ?>

My problem is that on custom fields I use this:

rating_average: %customfield(_glsr_average)%
rating_count: %customfield(_glsr_reviews)%

but it does not work

By another hand I would like to do this:

"aggregateRating": {
 "@type": "AggregateRating",
 "ratingValue": glsr_get_ratings(['assigned_posts' => 'post_id',]);
 "ratingCount": glsr_get_ratings(['assigned_posts' => 'post_id',]);
 },
}
</script>
<?php } ?>

But I have no idea that I am doing.

I would like your support. Thanks.

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