PDOStatement::execute(): MySQL server has gone away

<?php
namespace database;
 
use \PDO;
 
class Connection {
 
    private static $PDOInstance;
    private static $db_name = '****';
    private static $db_user = '*****';
    private static $db_pass = '*****';
    private static $stmt;
 
    static private $ConInstance;
 
    static public function getInstance() {
      if (!self::$PDOInstance) {
          self::$PDOInstance = new self;
      }
      return self::$PDOInstance;
    }
 
    private  function __construct() {
        try {
            $this::$ConInstance = new \PDO('mysql:host=localhost;dbname='.self::$db_name, self::$db_user, self::$db_pass);
            $this::$ConInstance->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
            $this::$ConInstance->setAttribute(PDO::ATTR_DEFAULT_FETCH_MODE, PDO::FETCH_ASSOC);
            $this::$ConInstance->exec('SET NAMES utf8');
 
        } catch (PDOException $e) {
            die("PDO CONNECTION ERROR: " . $e->getMessage() . "<br/>");
        }
    }
 
    private function __clone() {}
 
    private function __wakeup() {}
 
    private function __sleep() {}
 
    public function query($sql,$params = []){
        if(!is_array($params)){ $params = array($params); }
        try{
          self::$stmt = self::$ConInstance->prepare($sql);
          self::$stmt->execute($params);
          return self::$PDOInstance;
        }catch(PDOException $e){
          if($e->getCode() != 'HY000' || !stristr($e->getMessage(), 'server has gone away')) {
              die("PDO SQL ERROR: " . $e->getMessage() . "<br/>");
          }
          return $this->reconnect($sql,$params = []);
        }
    } 
 
    public function reconnect($sql, $params = []){
        self::$stmt = null;
        self::$PDOInstance = null;
        self::getInstance();
        return $this->query($sql, $params);
    }

$this::$ConInstance->query("SET wait_timeout=X");

new PDO('mysql:host=localhost;dbname=test;charset=utf8', $user, $pass);