How do i solve the problem when i need to convert mysql to mysqli

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PHP

MySQL

MySQL-Connector

hello i have problem when i need to convert my project from Mysql to Mysqli

this is the code, can any one help me?

<?PHP 
ob_start();

      require_once("../include/config.php"); //include"../include/config.php";
      require_once("../include/function.php");

define("uid",$_COOKIE['uid']);
define("login",$_COOKIE['login']);
define("type",$_GET['type']); 
 
 $QuerySelectU = mysqli_query("SELECT * FROM user WHERE u_id = '".uid."' ");
 $FetchObjectU = mysqli_fetch_object($QuerySelectU);
 
#============================[USER INFO]======================#
//es5raj elbyanat mn 8a3det elbyanat 3$an y6l3o bl user info
define("u_id",$FetchObjectU->u_id);
define("u_name",$FetchObjectU->u_name);
define("u_email",$FetchObjectU->u_email);

What I have tried:

convert my project from Mysql to Mysqli