Function to get YoastSEO Open Graph image from postmeta, falling back to post_thumbnail if it exists.

yoast-img.php

<?php
function yoast_og_img( $classes = '', $link = false, $size = 'medium_large' ) {

	$yoastImg = $yoastImgID = $post_thumb = false;
	$before = $after = null;

	$yoastImg = get_post_meta( get_the_ID(), '_yoast_wpseo_opengraph-image', true);
	$yoastImgID = attachment_url_to_postid( $yoastImg );
	$post_thumb = has_post_thumbnail( get_the_ID() );

	if( $yoastImg || $yoastImgID || $post_thumb ) {

		if( $link === true ) {

			$before = '<a href="'. get_the_permalink() .'" tabindex="-1" aria-hidden="true">';
			$after = '</a>';

		}

		if( $yoastImgID ) {

			$img = wp_get_attachment_image( $yoastImgID, $size, false, [ 'alt' => '', 'loading' => 'lazy', 'class' => $classes ] );

		} elseif( $yoastImg ) {

			$img = '<img src="'. $yoastImg .'" alt="" loading="lazy" class='. $classes .' />';
		
		} elseif( $post_thumb ) {
		
			$img = get_the_post_thumbnail( get_the_ID(), $size, [ 'alt' => '', 'loading' => 'lazy', 'class' => $classes ] );
		
		}

		echo $before . $img . $after;

	}
}