How to solve 'Undefined Index' Error from <input type="radio">?

Issue

Notice: Undefined index: gender in C:\xampp\htdocs\simv1\register.php on line 409

This my code so far :

<input type="radio" name="gender" value="Male">Male<br>
<input type="radio" name="gender" value="Female">Female

<?php if(isset($_POST['submit'])) {

   $a = $_POST['gender'];
   mysql_query("INSERT INTO register SET gender='$a');
}

?>

I've put if(isset()) on my PHP code but it not working.

I've read on Google before, I still confused. Can someone explain the problem with the solution?

Solution

This is one way to go. Also please do not use mysql as it is deprecated. Try using mysqli, or even PDO (I like PDO better).

Also, your SQL query is looking odd, so I have updated them as well.

<?php 
if(isset($_POST['gender'])) {

$a = $_POST['gender']; 

mysql_query("INSERT INTO register (gender) VALUES ('".$a."'"); //for insert

mysql_query("UPDATE register SET gender = '".$a."'"); // for update & don't forget to add the WHERE clause to avoid updating every record

} else {

$a = '';

}

?>

Answered By - Alex Szabo