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

Here is one my function what never fail.

I don't know why WordPress not made something like this before.

/**
    * Get current page ID
    * @autor    Ivijan-Stefan Stipic
    * @version  1.0.0
    **/
    function get_current_page_ID(){
        global $post, $wp_query;
        
        if(!is_null($wp_query) && isset($wp_query->post) && isset($wp_query->post->ID) && !empty($wp_query->post->ID))
            return $wp_query->post->ID;
        else if(function_exists('get_the_id') && !empty(get_the_id()))
            return get_the_id();
        else if(!is_null($post) && isset($post->ID) && !empty($post->ID))
            return $post->ID;
        else if('page' == get_option( 'show_on_front' ) && !empty(get_option( 'page_for_posts' )))
            return get_option( 'page_for_posts' );
        else if((is_home() || is_front_page()) && !empty(get_queried_object_id()))
            return get_queried_object_id();
        else if($this->get('action') == 'edit' &&  && isset($_GET['post']) && !empty($_GET['post']))
            return absint($_GET['post']);
        else if(!is_admin() && isset($_GET['p']) && !empty($_GET['p']))
            return absint($_GET['p']);
        
        return false;
    }

This function check all possible cases and return ID of the current page or false on the fail.