Doubt with login validation

Question

Good morning, I am developing a site for my TCC, and in it I try to make a login system with validation of user by levels.

Let’s assume if the user is administrator, when logging in he will check in the bd if the logged in user will have the field "type" != 2; if not it will go to normal user screen.

Below is the code I developed in php, but is showing error after trying to validate, it goes to a blank page;

    <?php
include("conexao.php");

$email = $_POST['email'];
$senha = $_POST['senha'];
/* Verifica se existe usuario, o segredo ta aqui quando ele procupa uma 
linha q contenha o login e a senha digitada */
$sql_logar = "SELECT * FROM aluno WHERE email = '$email' && senha = '$senha'";
$exe_logar = mysqli_query($conection, $sql_logar) or die (mysqli_error());
$fet_logar = mysqli_fetch_assoc($exe_logar);
$num_logar = mysqli_num_rows($exe_logar);

//Verifica se n existe uma linha com o login e a senha digitado
if ($num_logar == 0){
    session_start();
    $_SESSION['msg'] = "<div class='alert alert-danger'>Login ou senha incorreto!</div>";
    header("Location: index.php?login");
} 
else{
   //Cria a sessão e verifica tipo de login
    session_start();

    while($percorrer = mysqli_fetch_array($exe_logar) ){
    $tipo = $percorrer['tipo'];

    if($_SESSION['tipo'] != 2){
    $_SESSION['email'] = $email;
    $_SESSION['senha'] = $senha;
     header("Location: aluno.php");
    }
    }
}
?>

What can I do to make level validation work as planned?

Answer 1

Put the session_start(); only once at the beginning of the block:

<?php
session_start();
// resto do código

Do not use the operator && in Mysql, and yes the AND (see documentation).

Problem:

Put the if after the while, only that in the if you’re comparing a SESSION which apparently does not exist. You should compare the variable $tipo who had just declared, and needs a else if the if don’t get answered:

while($percorrer = mysqli_fetch_array($exe_logar) ){
   $tipo = $percorrer['tipo'];
}

$_SESSION['tipo'] = $tipo;

if($tipo != 2){
   $_SESSION['email'] = $email;
   $_SESSION['senha'] = $senha;
   header("Location: aluno.php");
}else{
   header("Location: administrador.php");
}

As SESSIONS email and senha will be created only for $tipo different than 2? Have to check this. If it is for any case, would have to stay like this:

while($percorrer = mysqli_fetch_array($exe_logar) ){
   $tipo = $percorrer['tipo'];
}

$_SESSION['tipo'] = $tipo;
$_SESSION['email'] = $email;
$_SESSION['senha'] = $senha;

if($tipo != 2){
   header("Location: aluno.php");
}else{
   header("Location: administrador.php");
}

Another thing, remove the line $fet_logar = mysqli_fetch_assoc($exe_logar); other than the $percorrer = mysqli_fetch_array($exe_logar) of while will be empty and the $tipo will have no value.