如何添加一個隨機名稱，使文件不會取代php

if(isset($_FILES['attachment'])){
      $errors= array();
      $file_name = $_FILES['attachment']['name'];
      $file_size =$_FILES['attachment']['size'];
      $file_tmp =$_FILES['attachment']['tmp_name'];
      $file_type=$_FILES['attachment']['type'];
      $file_ext=strtolower(end(explode('.',$_FILES['attachment']['name'])));
      
      $extensions= array("jpeg","jpg","png");
      
      if(in_array($file_ext,$extensions)=== false){
         $errors[]="extension not allowed, please choose a JPEG or PNG file.";
      }
      
      if($file_size > 2097152){
         $errors[]='File size must be excately 2 MB';
      }
      
   }
    $sql = $wpdb->prepare( "INSERT INTO ".$tablename." (post_id, name, email, price, author, post_title, purchase_type, closing_date, concessions_amount, insp_from, insp_to, seller_charge, emd, home_warranty, seller_occupancy, attachment ) VALUES ( %d, %s, %s, %d, %s, %s, %s, %s, %d, %s, %s, %d, %d, %s, %s, %s )", $id, $name, $email, $price, $author, $post_title, $purchase_type, $closing_date, $concessions_amount, $insp_from, $insp_to, $seller_charge, $emd, $home_warranty, $seller_occupancy, $file_name );
    
    
    
    if(empty($errors)==true){
        
          function tp_wordpress_uploads_directory_path() {
    $upload_dir = wp_upload_dir();
    return $upload_dir['basedir'] . "/offers/";
}
        $upload_check =  move_uploaded_file($file_tmp,tp_wordpress_uploads_directory_path().$file_name);
         
      }

現在系統正在替換現有的文件，是否有人可以幫助添加一個隨機數，以便文件名不匹配，可以通過將當前時間和日期添加到？我知道如何使用蘭德；可以工作，但無法在代碼中實現它。