[RESOLVED] PHP Error - Undefined index

rikalopes

Hello, I was wondering if anyone could help me with this error:

Notice: Undefined index: op in F:\xamp2\xampp\htdocs\Projecto\index.php on line 1

Notice: Undefined index: op in F:\xamp2\xampp\htdocs\Projecto\index.php on line 8

Here is the Code:

$op = $_GET['op'];
}

	//Corpo principal da pagina


	$op = $_GET['op'];
	if ($op=="REG")
	{
		if (!isset($_POST['controlo']))
		{
			formulario_registo();
		}
		 else {
			grava_utilizador();
		 }
	}
	elseif ($op == "LOG") {
		 $username = $_POST["username"];
		 $password = $_POST["password"];

		 #echo " Login:    " . $username . " <br>\n";
		 #echo " Password: " . $password . " <br>\n";

		 #liga&#65533;ao a bd
		 $ligaBD    = mysqli_connect('localhost','root','');
		 $escolheBD = mysqli_select_db($ligaBD, 'biblioteca');

		 #construcao da query:
		 $query_lista_user = "SELECT * FROM user WHERE
									  Username='"    .$username  . "' AND
									  password='" .$password . "';";
		 #echo $query_lista_user . " <br><br>" . "\n";

		 #executa query:
		 $resultado = mysqli_query($ligaBD, $query_lista_user);

		 #contar nr de linhas:
		 $num_linhas = mysqli_num_rows($resultado);

		 #echo "\t\tA base de dados retornou <b>" . $num_linhas . "</b> linha(s): <br>\n";
		 #comparar resultado:
		 if($num_linhas == 1) {
		   $dados = mysqli_fetch_array($resultado); #acede a cada linha devolvida
		   //echo "<b>Utilizador: </b>" . $dados['Username'] . "<br>\n";
		   //echo "<b>Password:   </b>" . $dados['Password'] . "<br><br>\n";
			#echo "Login efectuado com sucesso...<br>\n";
			session_start();
			$_SESSION["username"] = $username;
			$_SESSION["mensagem"] = "Login efectuado com sucesso...<br>\n";
			header("Location: index.php");
		 }
		  else echo "<b>Username/Password invalido(s)!</b> <br>\n";
		}[/QUOTE]

bradgrafelman

Welcome to PHPBuilder!

The error message is a result of code like this:

$op = $_GET['op'];

If no 'op' parameter was set in the query string, you're trying to reference an invalid index in the $_GET array. As such, you should always check to see if external data exists before referencing it, such as by using [man]isset/man or [man]empty/man.

One way to do this with little code is to use the ternary operator:

$op = isset($_GET['op']) ? $_GET['op'] : NULL;

which also allows you to set a default value (such as NULL) if the external data doesn't exist.

rikalopes

Thank you very much kind sir ! :-)

Problem solved !