PHP Get Url String If Statement

I want to create a Get Url String with an if statement.

Here is my code:

$value = $_GET['value'];
$fullname = "John Doe";
$email = "johndoe@email.com";

echo "value: " . $value;

if($value = "fullname")
    echo "fullname: " . $fullname;
elseif($value = "email")
    echo "email: " . $email;
else
    echo "fullname: " . $fullname;
    echo "<br>";
    echo "email: " . $email;

It returns both fullname and email each time even if I enter only the fullname or email value. What am I doing wrong? Thanks