Another option to use @ in PHP?

@ is not a good practice, although it may be used, what is recommended for doing variable checks is isset .

isset other than array_key_exists (which can also be used as the example of Ricardo) supports multidimensional checks and you can also check more than one variable at a time, for example:

• Checking multidimensional arrays:

  <?php
  $test = array('a' => 1);
  
  var_dump(isset($test['a']['b'])); //Retorna bool (false)
  var_dump(isset($test['a']));      //Retorna bool (true)
  

• Checking more than one variable at a time:

  <?php
  $a = 1;
  var_dump(isset($a)); //Retorna bool (true)
  var_dump(isset($a, $b)); //Retorna bool (false) por que $b não existe
  

  or

  <?php
  $a = array('test' => 1);
  $b = array('foo'  => 2);
  
  var_dump(isset($a['test'])); //Retorna bool (true)
  var_dump(isset($a['test'], $b['test'])); //Retorna bool (false) por que $b['test'] não existe
  

isset also supports stdClass (or variables of a class)

Details about the isset:

<?php
$a = NULL;
var_dump(isset($a)); //Retorna bool (false)

empty vs isset

You may not want to check multiple variables at the same time, as in the example above isset ( isset($a, $b, $c, $d, $e) ), you can use empty , which in addition to verifying if the "variable exists" it also checks if it is empty in case of strings for example. Situations that empty will return TRUE :

• "" (an empty string)
• 0 (when an integer equal to zero)
• "0" (zero as string)
• NULL
• FALSE
• array() (an empty array)
• var $var; (When a variable is declared in a class but has no value since it is NULL)

The question problem

How to suppress all notifications of undeclared variables without using @ ? In this case I would recommend using isset and creating normal variables, such as:

$variavelA = empty($_SESSION['varA']) ? NULL : $_SESSION['varA'];
$variavelB = empty($_SESSION['varB']) ? NULL : $_SESSION['varD'];
$variavelC = empty($_SESSION['varC']) ? NULL : $_SESSION['varC'];
$variavelD = empty($_SESSION['varD']) ? NULL : $_SESSION['varD'];

If it sounds cumbersome, you can use a loop with foreach or for , it's a bit tricky to admit, but there are different ways to do the process, this is just one and it will depend on how your code is :

$keys_in_session = array('a', 'b', 'user', 'ultimaatividade');

foreach ($keys_in_session as $k => $v) {
    if (empty($_SESSION[$v])) {//Acaso a variável não exista na sessão ele cria ela como o valor 'NULL' para que você possa usa-la sem ocasionar
        $_SESSION[$v] = NULL;
    }
}

Consideration of use

Despite the example with foreach , I personally recommend using only isset and empty combined with if or with ternary comparison operators:

echo 'Resposta: ', ( empty($_SESSION['message']) ? 'sem resposta' : $_SESSION['message'] );

Development Environment vs. Production Environment

As already mentioned in the other answer, the use of error_reporting is a good practice for the production and development environment.

• Development environment is when you are developing the software in a place where it does not affect the server / site ie on your machine for example.

I personally always use all "on" error notifications in the development environment:

<?php
//No topo do script
error_reporting(E_ALL|E_STRICT);

In the production environment I always turn off all errors:

<?php
//No topo do script
error_reporting(0);

But it is not possible to determine all failures that may occur and all situations, so how do you know which errors occurred? For this we have 3 functions that we can use combined, error_get_last() , set_error_handler and register_shutdown_function , so you can write errors to a .txt file for example and refer to this file to check when the fault occurred, see an example in this other answer:

link

  

Note: It's not because you're going to turn off error messages that you should not use isset or empty , try to use E_ALL|E_STRICT to detect possible code faults and then fix them.

  

With this solution you check whether the key of the session (or any other) array exists.

if (array_key_exists("login", $_SESSION)) {
    echo "O Usuario esta logado";
}

  

With this solution, no more notices will be displayed as Unexpected Index (that's what the question asks) but does not resolve Unexpected Index .

To configure php.ini to not display notification messages, you should leave it as follows:

error_reporting  =  E_ALL & ~E_NOTICE

Another way is to paste this line into the start file of the .php file:

ini_set("display_errors", "0");

Another way is to paste this line into the start file of the .php file:

error_reporting(E_ALL ^ E_NOTICE); // ira reportar todos esceto os 'notices'.

Follow the session_defs.php file to be included in the code setup. In this file I created the session_def function, which defines the default value for the session variable if it has not yet been defined.

Session_defs.php file

<?php
function session_def($name, $value) {
    // isset: Informa se já variável foi iniciada antes
    if (!isset($_SESSION[$name]))
        return $_SESSION[$name] = $value; // Se não foi iniciada,
                                          // inicia com o valor padrão
    return $_SESSION[$name];
}

// Cria a sessão ou resume a sessão atual.
// A partir deste ponto a variável $_SESSION é definida com os valores
// que já foram definidos anteriormente.
session_start();

// Define os valor padrão para as variáveis de sessão que não foram iniciadas
// com session_start.
session_def('item1', 12345);
session_def('item2', true);
session_def('item3', 'string');

?>

Use

<?php
require_once 'session_defs.php';
?><!doctype html>
<html>
<head>
    <meta charset="utf-8">
</head>

<body>
<pre>
<?php
var_dump($_SESSION); 
?>
</pre>

</body>
</html>

Normally this undefined index error is caused by problems in $ _POST or $ _GET.

You can execute extract (); at the beginning of the code. So all variables come in automatically, without having to call $ _POST or $ _GET.

Just insert at the beginning of the code:

extract();

This article explains in detail the solution to the error:

link