PHP - Undefined variable

Question

I\'m doing some exercises from Beginners PHP & MySQL by Mr. Tucker.

On his example everything works fine, but on my PC there is an error:

Answer 1

You are trying to access the variable $passwordRetrieved when it has not yet been given a value. The access is done here:

echo "passwordRetrieved = ".$passwordRetrieved."
";

The variable would be set just above:

while ($row = mysql_fetch_array($tUser_SQLselect_Query, MYSQL_ASSOC)) {
    $passwordRetrieved = $row['password'];  // VARIABLE SET HERE
}

The important thing is that the variable only gets set if the query returns a matching row (i.e., on a successful login). If the login is not valid, the variable is not set.

To check if a variable is set without getting a notice, you would use either isset or empty (there are subtle differences, but as a rule of thumb you can use either most of the time). Your code actually already does this just below:

// Checking if $passwordRetrieved has been set using empty()
if (!empty($passwordRetrieved) AND ($password == $passwordRetrieved)) {