Wordpress get_the_ID() returns 0

Question

function post_like(){ 
    global $wpdb;
    $c = $_POST['next']; 
    echo $c; 
    $d = get_the_ID();
    $wpdb->insert('wp_likes',
        array(
            'article_id' => $d,
            'user_id' => '1'
        )
    );
    die(); 
}

and my ajax.js file:

function Click_Me() {
    var className = jQuery('#flag').attr('class');
    if (className == "like") {
        var temp = "unlike";
    } else {
        var temp = "like";
    }

    jQuery.ajax({
        url: like.ajax_url,
        dataType: 'html',
        data: {
            action: 'post_like',
            next: temp
        },
        success: function() {
            jQuery('#flag').attr('class', temp);
            jQuery('#sonuc').html(temp);
        }
    });
}

If I want to get id with this method

$a = get_the_ID();
$a variable's value == 0

Why? I tried other tricks for getting id, but methods do not works. I think the problem is ajax but I don't understand why... Thanks for answers.

Answer 1

You can make a global post and fetch its id. Like:

global $post;
$d = $post->ID;

If you don't want to do it this way. You can simply pass the id value to ajax data.

Answer 2

If your user id returns 0, you should be use this metod : intval();

Because during wordpress coding, table type int : %d so it's must be integer.

For Example(Ajax) :

$user_id = intval( $_POST['user_id'] );

Answer 3

You can simply create a function with global $post as an argument.

function post_like($post){ 
    global $wpdb;
    $c = $_POST['next']; 
    echo $c; 
    $d = $post->ID
    $wpdb->insert('wp_likes',
        array(
            'article_id' => $d,
            'user_id' => '1'
        )
    );
    die(); 
}