How to get current post_id in function.php file

Question

This is my function in function.php file

  function getcity(){
    global $wpdb;

    if($_POST[\'state\'])
            {
                $id=$_POST[\'state\         


        

Answer 1

Note that $post or get_queried_object_id() do not work until the first query was fired. So this options are available only at the hook template_redirect and later. But functions.php is included much earlier (before the hook after_setup_theme) so this isn't a solution.

A function that should work pretty much anywhere would be

$url = 'http://' . $_SERVER[ 'HTTP_HOST' ] . $_SERVER[ 'REQUEST_URI' ];
$current_post_id = url_to_postid( $url );

Here is a overview over hook execution order.

If your code is executed after the template_redirect hook these option may be better:

global $post;
$id = $post->id;

or

$id = get_queried_object_id();