问AJAX不向PHP文件发送任何内容

EN

$('#preregister').submit(function () {


    if(checkemail("prereg_email")) {

        var data;

        data = $(this).serialize();
        console.log(data);

        $('#imageloader').fadeIn();
        $.ajax({
            url: '/docs/adduser.php',
            data: data,
            processData: false,
            contentType: false,
            type: 'POST',
            success: function ( data ) {
                //console.log(data); //returns a string of the data.
                var data = JSON.parse(data); //parses the string into an object.
                console.log(data); //logs the object.
                if (data.error) { alert(data.message); }
            }

        });

    }

      return false;
    });

<?php

    $Return = array();
    $Return["in"] = $_POST;
    $Return["error"] = false;
    $Return["message"] = "Nothing has happened.";

    /* EMAIL */
    $in_email = urldecode($_POST["prereg_email"]);
    $Return["in_email"] = $in_email;

    if (!filter_var($in_email, FILTER_VALIDATE_EMAIL)) {

        $Return["error"] = true;
        $Return["message"] = "Enter a valid email.";

    }

    if (!$in_email) {

        $Return["error"] = true;
        $Return["message"] = "Enter an email.";

    }


    str_replace('\\/', '/', json_encode($Return));
    echo json_encode($Return);

?>