Pass PHP variable back to jQuery $.ajax function

1. HTML I have an input requesting the user to enter their PIN code: `<input type="text" name="pin" maxlength="4" id="pin" />` 2. javaScript When the user types in 4 characters, the jQuery function fires off an ajax call to process the PIN in a PHP file and return the corresponding site name: ``` $("input#pin").keyup(function() { var PIN = $("this").val(); if (PIN.length == 4) { var dataString = "PIN=" + PIN; $.ajax({ type: "POST", url: "pins.php", dataType: "json", data: dataString, cache: false, success: function(site) { console.log("site name is:" + site); } }); } }); ``` 3. PHP `pins.php` contains the following code: ``` <?php $pin = $_POST["PIN"]; if ($pin == "faf9") { $site = "pgv"; } echo $site; ?> ``` Problem I cannot seem to get the value of `$site` back into the success function of the ajax call. Console log reports `null` as the value if the pin doesn't equal `faf9` and there is no log if I enter the correct pin. I can't seem to figure out where I'm going wrong?