wordpress get post id

1// Retrieve the ID of the current item in the WordPress Loop.
2get_the_ID()

1function get_the_ID() { // phpcs:ignore WordPress.NamingConventions.ValidFunctionName.FunctionNameInvalid
2    $post = get_post();
3    return ! empty( $post ) ? $post->ID : false;
4}
5

1$post   = get_post( 123 ); // Where 123 is the ID
2$output =  apply_filters( 'the_content', $post->post_content );

1get_posts(array(
2    'fields'          => 'ids', // Only get post IDs
3    'posts_per_page'  => -1
4));
5

1url_to_postid( site_url('the_slug') );
2

1//WordPress: Query a specific post by its post type & ID
2//For example, query Case Study with ID #12345
3
4<?php query_posts('post_type=case_studies&p=12345'); ?>
5  
6/*To determine a post ID, refer to the
7URL of the post while editing it:
8http://localhost...wp-admin/post.php?post=12345...*/