Having trouble figuring out my error. Trying to scrub form data before I submit for SQL injections, and I am not getting any information to pass through to database. I have everything in one document, and the form-action is referencing the right page. I have also triple-checked the DB table, and it is correct as well. Also, if you have any other suggestions for SQL injection handling, it would be appreciated.
 <?php
 if(isset($_POST['submit'])) {
 //database connection
 include_once("include-php/db-conx-local.php");
 //gather variables from form and scrub
 $name = preg_replace('#[^a-z0-9]#i', 3'', $_POST['name']);
 $email = mysqli_real_escape_string($db_conx, $_POST['email']);
 $subject = preg_replace('#[^a-z0-9]#i', '', $_POST['subject']);
 // Function to get the client IP address
 $ip = getenv('HTTP_CLIENT_IP')?:
        getenv('HTTP_X_FORWARDED_FOR')?:
        getenv('HTTP_X_FORWARDED')?:
        getenv('HTTP_FORWARDED_FOR')?:
        getenv('HTTP_FORWARDED')?:
        getenv('REMOTE_ADDR');
 // FORM DATA ERROR HANDLING
 if($name == "" || $email == "" || $subject == ""){
    echo "Please fill out the entire form.";
    exit();
 } else {
    $sql = "INSERT INTO emailContactForm (name, email, subject, ip, postDate)
    VALUES ('$name', '$email', '$subject', '$ip', now())";
    mysqli_query($db_conx, $sql);
 }
 exit();
 }
 ?>
<form action="contact.php" method="post" id="contact-form">
            <div class="input-prepend">
                <span class="add-on"><i class="icon-user"></i></span>
                <input class="span4" id="name" name="name" size="16"
type="text" placeholder="Name">
            </div>
            <div class="input-prepend">
                <span class="add-on"><i class="icon-envelope"></i></span>
                <input class="span4" id="email" name="email" size="16"
type="text" placeholder="Email Address">
            </div>
            <textarea class="span6" id="subject" name="subject"></textarea>
            <div class="row">
                <div class="span2">
                    <input type="submit" id="submit" class="btn btn-inverse"
value="Send Message">
                </div>
            </div>
        </form>
