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.

Answer 2

You want the global variable $post as documented here:

http://codex.wordpress.org/Global_Variables

Declare the $post global like so:

global $post;

Then you should be able to access the id of the post using $post->ID.

Here is a more complete doc of the attributes available through the $post global: http://codex.wordpress.org/Function_Reference/$post

Answer 3

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();