如何用php在mysql中存储数据

So, i just started learning php and I can't figure out what I doing wrong, data doesn't register to database on mysql. I am using xampp. All names and data are written right. I checked all functions... Still doesn't work.

<DOCTYPE html>
<html>
  <head>
      <title>New Account</title>
  </head>
  <body>
  <?php
              /*
             Implementare:
             -functie de verificare daca functia exista in baza de date
             -function bool_email($POST_('email adress'))
             -functie comparare stringuri
             */
  $name = '';
  $password = '';
  $gender = '';
  $email = '';
  $tc = '';
  if(isset($_POST['submit']))
  {
      $ok = true;

      if(!isset($_POST['name']) || $_POST['name'] === '' /*bool_name_exist($the string)*/)
      {
          $ok = false;
          printf("You forget about name or it exist already in the database!");
          echo '<br>';
      }
      else
      {
          $name = $_POST['name'];
      }
      if(!isset($_POST['password']) || $_POST['password'] === '' )
      {
          $ok = false;
          printf('You forget about password!');
          echo '<br>';
      }
      else
      {
          $password = $_POST['password'];
      }
      if(!isset($_POST['password_conf']) || $_POST['password_conf'] === '' || strcmp($_POST['password'], $_POST['password_conf']) != 0)
      {
          $ok = false;
          printf('You forget about password or password conf. does not match!');
          echo '<br>';
      }


      if(!isset($_POST['email']) || $_POST['email'] === '' /*functie care verifica daca emailul e valid sau este in baza de date*/)
      {
          $ok = false;
          printf('You forget about email or your email address is not validate!');
          echo '<br>';
      }
      else
      {
          $email = $_POST['email'];
      }
      if(!isset($_POST['gender']) || $_POST['gender'] === '')
      {
          $ok = false;
          printf('You forget about gender!');
          echo '<br>';
      }
      else
      {
          $gender = $_POST['gender'];
      }
      if(!isset($_POST['tc']) || $_POST['tc'] === '')
      {
          $ok = false;
          printf('You need to validate t&c!');
          echo '<br>';
      }
      else
      {
          $tc = $_POST['tc'];
      }
      if($ok === true)
      {
      printf('your account has been registered');
      }
      if($ok)
      {
          $db = mysqli_connect('localhost', 'root', '', 'platformaworkout');
          $sql = sprintf("INSERT INTO registerdata (Name, Gender, Password, Email), VALUES ('%s', '%s', '%s', '%s') ",
              mysqli_real_escape_string($db, $name),
              mysqli_real_escape_string($db, $gender),
              mysqli_real_escape_string($db, $password),
              mysqli_real_escape_string($db, $email));
          printf('<br>%s', $sql);
          if(mysqli_query($db, $sql))
          {
              echo '<br>it work';
          }else
          {
              echo '<br>I want to kill myself...';
          }
          mysqli_close($db);
          echo '<p>user added</p>';
      }
  }
  ?>
  <form method="post" action="">
      <header>Register new account:<br></header>
      UserName:<input type="text" name="name" value="<?php echo htmlspecialchars($name); ?>"><br>
      Password:<input type="password" name="password" value="<?php echo htmlspecialchars($password); ?>"><br>
      Password confirmation:<input type="password" name="password_conf"><br>
      Gender:
        <input type="radio" name="gender" value="f" <?php if($gender === 'f'){echo 'checked';}?>>female
        <input type="radio" name="gender" value="m" <?php if($gender === 'm'){echo 'checked';}?>>male<br>
      Email Address:<input type="text" name="email" value="<?php echo htmlspecialchars($email); ?>"><br>
      <input type="checkbox" name="tc" value="ok" <?php if($tc === 'okay'){echo 'checked';}?>>I accept t&c!<br>
      <a src="#">Read t&c!</a>
      <input type="submit" name="submit" value = "submit">
  </form>
  </body>
</html>

What I see in the browser My database structure

</div>

Maybe you forgot the action part:

 <form method="post" action="echo $_SERVER['PHP_SELF'];">

INSERT INTO registerdata (Name, Gender, Password, Email), VALUES ('jarlio', 'm', 'leaf', 'somemail@gmail.com') , is not a correct command in sql because of that "," before "VALUES". Find it, thanks for help anyway