Multiple Custom Fields

Hi @mian117,

Making changes to plugin’s code (or to a third-party theme) is not a good WordPress development practice: the next time you update the plugin WordPress will replace your modified plugin files with the stock ones automatically, undoing all of your plugin modifications.

Instead, please use the built-in hooks that the plugin provides so you can make changes to it without having to modify its code – like so for example:

<?php
/**
 * Renders an alternative thumbnail from a custom field
 * if the post doesn't have a thumbnail.
 *
 * @author Hector Cabrera
 * @see    https://www.ads-software.com/support/topic/multiple-custom-fields-10/
 *
 * @param  string  $img_url  The default 'No thumbnail' image URL
 * @return string  $img_url  The (modified) 'No thumbnail' image URL
 */
function wpp_thumbnail_fallback( $img_url, $post_id ) {

    // Post  doesn't have a thumbnail so let's fallback 
    // to the custom field one
    if ( ! has_post_thumbnail( $post_id ) ) {
        // Get the image URL from your custom field here
        // and then assign it to $img_url or return your URL
        //
        // eg. $img_url = get_post_meta( $post_id, 'MY_CUSTOM_FIELD_IMG_URL', true );
    }

    return $img_url;

}
add_filter( 'wpp_default_thumbnail_url', 'wpp_thumbnail_fallback', 10, 2 );

If you have any other questions don’t hesitate to ask, ok?

I’m impressed with this fast response. Thank You very much.
This solution solved the problem. I have tweaked it a bit to work as per my requirement for more than 1 custom field.

/**
 * Renders an alternative thumbnail from a custom field
 * if the post doesn't have a thumbnail.
 *
 * @author Hector Cabrera
 * @see    https://www.ads-software.com/support/topic/multiple-custom-fields-10/
 *
 * @param  string  $img_url  The default 'No thumbnail' image URL
 * @return string  $img_url  The (modified) 'No thumbnail' image URL
 */
function wpp_thumbnail_fallback( $img_url, $post_id ) {

    // Post  doesn't have a thumbnail so let's fallback 
    // to the custom field one
    if ( ! has_post_thumbnail( $post_id ) ) {
        // Get the image URL from your custom field here
        // and then assign it to $img_url or return your URL
		if( get_field('graphic_910x512', $post_id) ){
          		$image_url_linkedin = get_field('graphic_910x512', $post_id);
				$img_url =  $image_url_linkedin['url'];
		}
		else if( get_field('graphic_683x512', $post_id) ){
          		$image_url_linkedin = get_field('graphic_683x512', $post_id);
				$img_url =  $image_url_linkedin['url'];
		}
		else if( get_field('xxl_graphic', $post_id) ){
          		$image_url_linkedin = get_field('xxl_graphic', $post_id);
				$img_url =  $image_url_linkedin['url'];
		}
		
    }

    return $img_url;

}
add_filter( 'wpp_default_thumbnail_url', 'wpp_thumbnail_fallback', 10, 2 );