PHP - Why This Return -2.8421709430404e-14 ?

<?php

class Article{
    public function fetch_all(){
        global $pdo;

        $query = $pdo->prepare("SELECT * FROM `articles` ORDER BY `article_timestamp` DESC");
        $query->execute();

        return $query->fetchAll();
    }

    public function fetch_data($article_id){
        global $pdo;

        $query = $pdo->prepare("SELECT * FROM `articles` WHERE `article_id` = ?");
        $query->bindValue(1, $article_id);
        $query->execute();

        return $query->fetch();
    }

    /*
     * These have gotten added later on.
     */
    
    public function delete($id){
        global $pdo;

        $query = $pdo->prepare("DELETE FROM `articles` WHERE `article_id` = ?");
        $query->bindValue(1, $id);
        $query->execute();

        // The "return" here.

    }

    public function edit_page($title, $content, $aticle_id){
        global $pdo;

        $query = $pdo->prepare("UPDATE `articles` SET `article_title` = ?, `article_content` = ? WHERE `article_id` = ?");

        $query->bindValue(1, $title);
        $query->bindValue(2, $content);
        $query->bindValue(3, $article_id);

        $query->execute();

        // The "return" here.
    }

}


?>