nl_amp_set_schema_type.php

<?php
function nl_amp_set_schema_type( $metadata, $post ) {
	if ($post->post_type == 'recipe') {

		$metadata['@type'] = 'Recipe';
		$metadata['name'] = $post->post_title;
		
		$metadata["recipeYield"] = get_field('new_serves', $post->ID);
		$metadata['description'] = get_field('description', $post->ID);

		// Prep Time
		if (get_field('prep_time_hours') OR get_field('prep_time_minutes')) {
			$prep_duration = 'PT';
			if (get_field('prep_time_hours')) {
				$prep_duration .= get_field('prep_time_hours') . 'H';
			}
			if (get_field('prep_time_minutes')) {
				$prep_duration .= get_field('prep_time_minutes') . 'M';
			}
			$metadata['prepTime'] = $prep_duration;
		}

		// Cook Time
		if (get_field('cook_time_hours') OR get_field('cook_time_minutes')) {
			$cook_duration = 'PT';
			if (get_field('cook_time_hours')) {
				$cook_duration .= get_field('cook_time_hours') . 'H';
			}
			if (get_field('cook_time_minutes')) {
				$cook_duration .= get_field('cook_time_minutes') . 'M';
			}
			$metadata['cookTime'] = $cook_duration;
		}

		// Get Total Time
		$total_duration = false;
		if ($prep_duration OR $cook_duration) {
			$e = new DateTime('00:00');
			$f = clone $e;
			if ($prep_duration) {
				$p = new DateInterval($prep_duration);
				$e->add($p);
			}
			if ($cook_duration) {
				$c = new DateInterval($cook_duration);
				$e->add($c);
			}
			$metadata['totalTime'] = $f->diff($e)->format("PT%hH%iM");
		}
		elseif (get_field('new_time')) {
			$i = DateInterval::createFromDateString(get_field('new_time'));
			$metadata['totalTime'] = $i->format("PT%hH%iM");
		}
			
		if ($recipe_category = get_yoast_primary_category('recipe_categories')) {
			$metadata['recipeCategory'] = $recipe_category;
		}

		if ($calories = get_field('calories')) {
			$metadata['nutrition']['@type'] = 'NutritionInformation';
			$metadata['nutrition']['calories'] = $calories . ' calories';
		}

		while (have_rows('new_ingredients', $post->ID)) { the_row();
			$metadata['recipeIngredient'][] = get_sub_field('quantity') . ' ' . get_sub_field('ingredient');
		}

		$instructions = '';
		$i = 1;
		while (have_rows('directions', $post->ID)) { the_row();
			$instructions .= $i++ . '. ' . get_sub_field('step') . '\n';
		}
		$metadata['recipeInstructions'] = $instructions;

		// $metadata['aggregateRating'] = array(
		// 	'@type' => 'AggregateRating',
		// 	'ratingValue' => the_ratings($post->ID)
		// );
	}
    
    return $metadata;
}
add_filter( 'amp_post_template_metadata', 'nl_amp_set_schema_type', 10, 2 );