从用户表中删除行PHP MYSQL

我认为您的问题是您的表单操作(teams.php)将收到帖子数据.您的删除代码在同一个文件上,逻辑上$ _POST ['leave']将永远不会在此页面中设置.

只是尝试在您的表单操作属性中删除您的teams.php.

或者在teams.php文件中添加删除代码

//Make sure you have started the session before using it
$user_id = $_SESSION['user_session'];

if(isset($_POST['leave'])){
    $stmt = $DB_con->prepare("DELETE FROM users WHERE user_id = $user_id ");
         $stmt->execute();
}

另一条建议是使用参数化查询.例:

if(isset($_POST['leave'])){
  $stmt = $DB_con->prepare("DELETE FROM users WHERE user_id = ? ");
         $stmt-> bindParam(1,$user_id);
         $stmt->execute();

}