I have some issues in my login form,how to resolve it?

Question

I put in the information and click "Submit Query" to log in, it redirects me to a blank page.

• I have already registered with the information im trying to login.

• And checked in the database if the user exists. This is the code:

  <?php
  // ERROR DEBUG THINGY
  $showErrors = (isset($_GET['debug'])) ? true : false;
  
  if(!$showErrors) {
      ini_set('display_errors', 'Off');
  }
  else {
      error_reporting(E_ALL);
      ini_set('display_errors', 'On');
  }
  
  // DATABASE START
  $servername = "localhost";
  $username = "root";
  $conn = mysql_connect($servername, $username) or die (mysql_error());
  mysql_select_db("test", $conn);
  
  // WE START THE SESSION
  session_start();
  
  // START LOGIN PROCESS
  if(isset($_SESSION['logged'])) {
      print_secure_content(); //CONTENT THAT'S ECHOED ONCE YOU LOG IN
  }
  else {
      if(!$_SESSION['logging']) {       //IF LOGGING SESSION ISNT RUNNING
          $_SESSION['logging'] = true; //RETURNS THE USER BACK TO THE LOGIN FORM
          loginform();                //SHOWS THE LOGIN FORM
      }
      else if($_SESSION['logging']) {
          $numberOfRows = checkpass(); //CHECK IF THE USER ALREADY EXISTS
          if($numberOfRows == 1) {    //IF OLD USER LOG HIM IN
              $_SESSION['id'] = $_POST['username'];
              $_SESSION['logged'] = true;
              echo "<h1> You have logged in successfully </h1>";
              print_secure_content();
              print_user_details();
          }
          else {
              echo "You have entered a wrong username or password, please try again.<br />";
              loginform();
          }
      }
  }
  
  // DATABASE CLOSE
  mysql_close();
  
  // FUNCTIONS!!!
  
  function loginform() { //THE LOG IN FORM
      echo "Please login <br />
      <form method=\"POST\" action=\"?\">
              USERNAME<br />
              <input name='username' type='text'><br />
              PASSWORD<br />
              <input name='password' type='password'><br />
      <input type='submit' name='login'></form>
      <p><a href='registerform.php'> Register Here! </a></hr>";
  }
  
  function print_user_details() { //CHECK PASSWORD
      if(isset($_POST['username']) && isset($_POST['password'])) {
          $sql = "SELECT * FROM users WHERE name = '{$_POST['username']}' and password = '{$_POST['password']}'";
          $result = mysql_query($sql, $conn) or die (mysql_error());
          return mysql_num_rows($result);
      }
  }
  
  function checkpass() { //CHECK PASSWORD
      if(isset($_POST['username']) && isset($_POST['password'])) {
          $sql = "SELECT * FROM users WHERE name = '{$_POST['username']}' and password = '{$_POST['password']}'";
          $result = mysql_query($sql, $conn) or die (mysql_error());
          return mysql_num_rows($result);
      }
  }
  
  function print_secure_content() { // ECHO ONCE YOU LOG IN
      echo 'Hello '. $_SESSION['id'] .'!<br />';
      echo 'Only a logged in user can see this. <br /> <a href="logout.php"> Logout </a>';
  }
  

  ?>

Answer 1

There might be some syntax Error.

Go to php.ini file
Change display_errors=off to on and save it.
Restart the server
Check in Front end. You might find the Error. Correct it.
Again Restart the Server to see your changes.

Answer 2

$sql = "SELECT * FROM users WHERE name = '".$_POST['username']."' and password = '".$_POST['password']."'";

user sql query like this