Source

File: wp-includes/post.php

function get_pung( $post_id ) {
	$post = get_post( $post_id );
	if ( ! $post ) {
		return false;
	}

	$pung = trim( $post->pinged );
	$pung = preg_split( '/\s/', $pung );

	/**
	 * Filters the list of already-pinged URLs for the given post.
	 *
	 * @since 2.0.0
	 *
	 * @param string[] $pung Array of URLs already pinged for the given post.
	 */
	return apply_filters( 'get_pung', $pung );
}