WordPress Options Framework, and Polylang - given a post ID, return a URL for a default image specified in admin options.

fn-get-default-image-for-post.php

unction get_default_image_for_post($post_id){

	if(!$post_id) { return false; }

	global $smof_data;
	//error_log('smof_data:');
	//error_log(print_r($smof_data,true));

	$thumb_url = false;
	$prefix = 'mxp_';

	$key_cat_news = $prefix . 'category_news';
	$key_cat_blog = $prefix . 'category_blog';


	$key_img_news = $prefix . 'img_default_news';
	$key_img_blog = $prefix . 'img_default_blog';

	$keys_to_search = [ $key_cat_news => $key_img_news, $key_cat_blog => $key_img_blog ];
	$post_categories = wp_get_post_categories( $post_id );

	foreach ($keys_to_search as $key_category => $key_image) {

	    // do we have a category set as a 'blog' category in the admin?
		if(array_key_exists($key_category, $smof_data) && $smof_data[$key_category]) {

	    	error_log('news category slug: ' . $smof_data[$key_category]);

	    	// get ID of the category in question
	    	$theCatId = get_term_by( 'slug', $smof_data[$key_category], 'category' );

			if(property_exists($theCatId, 'term_id')) {

				error_log('category object based on slug:');
				error_log(print_r($theCatId->term_id, true));

				// get ID of the translation:
				$translated_term_id = get_id_of_translated_category($theCatId->term_id);
				error_log('translated term: ' . $translated_term_id);

				$first_check = array_search($theCatId->term_id, $post_categories);

				// error_log(print_r($first_check, true));

				if( array_search($theCatId->term_id, $post_categories) !== false || ($translated_term_id !== false && array_search($translated_term_id, $post_categories)) ) {

					error_log('the post has a category that we are interested in.');

					// see if have default image for articles of this category
					if( array_key_exists($key_image, $smof_data) ) {
						error_log( 'have ' . $key_image . ' in smof_data...' );
						if( $smof_data[$key_image] ) {
							error_log( $key_image . ' in smof_data is not empty!' );
							$thumb_url = $smof_data[$key_image];
							//error_log('default image does exist: ' . $thumb_url);
						} else {
							error_log('nope 5');
							$thumb_url = get_stylesheet_directory_uri() . '/img/' . $key_image .  '.jpg';
						}
					} else {
						$thumb_url = get_stylesheet_directory_uri() . '/img/' . $key_image .  '.jpg';
						error_log('nope 4');
					}

				} else {
					error_log('nope 3');
				}

			} else {
				error_log('nope 2');
			}

	    } else {
			//error_log('nope 1');
	    }

	}

	return $thumb_url;
}