isset PHP5 is facultative or not

Question

Why we use isset here with !empty ?
Is it necessarily to use it because isset check whether the variable is set or not and $_POST is a superglobal variable already set.

 <?php
    include 'Config.php';
    $email  = "";
    $mdp    = "";
    $e = array();
    if(isset($_POST))
    {
     if(!empty($_POST))
     {
      $email  = $_POST['adresse_email'];
      $mdp    = $_POST['motpasse'];
   ...

Answer 1

isset() checks if the variable exists, but not it's content.

You use empty() later to check if it's an empty string.

In this case, since $_POST is an array, and you're not saying which position to pick the value from, empty() will check if the array contains any positions.

---

As mentioned in the comments by Armen , those two verifications are pointless. You could simply check if the request method of the script is POST

 if ($_SERVER['REQUEST_METHOD'] === 'POST') 

Answer 2

In your example isset() is used to check if the $_POST superglobal variable is set, but it's redundant code. empty() already includes the functionality of isset() but also does more. From the documentation:

Returns FALSE if var exists and has a non-empty, non-zero value. Otherwise returns TRUE.

The following things are considered to be empty:

 "" (an empty string) 0 (0 as an integer) 0.0 (0 as a float) "0" (0 as a string) NULL FALSE array() (an empty array) $var; (a variable declared, but without a value) 

... so it will also check if the $_POST array has elements in it (is not an empty array).

For a simple web form checking, using !empty($_POST) is easier than writing $_SERVER['REQUEST_METHOD'] === 'POST' , but the result is the same, if the request was not made through POST, none of them will match.

Additionaly, in your code, you could use isset() on the $_POST elements also to rule out the warnings issued by PHP if an index is not defined (if an element wasn't submitted in the form):

$email  = isset($_POST['adresse_email']) ? $_POST['adresse_email'] : '';
$mdp    = isset($_POST['motpasse']) ? $_POST['motpasse'] : '';