Solved: How to hide contact form only if no validation errors

I am getting confused by all these different variations i.e.: success/done/promise and can't figure out how to change this code so that if there are validation errors, the form will not disappear but if there are no validation errors and the form is submitted, then the success message must appear and the form disappears. Currently, whether validation errors or none, the validation/success message shows and the form disappears.

This question already has an answer here:
what is difference between success and .done() method of $.ajax 4 answers
I want the form to still show and allow input if a failed validation occurs but if all succeeds then I want the success message to show and the form to disappear. This code hides the form whether success or validation errors occur.

$(document).ready(function(){
        $( "#send" ).click(function(e){
            e.preventDefault();
            $( "#send" ).prop( "disabled", true );
            $( ".hideloader" ).show();
            $( "#send" ).html( "Sending <img src='img/ajax-loader.gif'>" );
            var form_data = $( "#contact-form" ).serialize();
            $.ajax({
                type: 'POST',
                url: 'contact-submit.php',
                data: form_data
            }).done(function(response) {
                $( "#server-results" ).hide().html(response).fadeIn("slow");
                $( "#send" ).prop("disabled", false);
                $( "#send" ).html( "Send Enquiry" );
                $( "#contact-form" ).hide();
        });
    });
});

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My php code just using an email field as an example looks like this:

if ($_SERVER["REQUEST_METHOD"] === "POST") {

$message = "";

if(filter_var($_POST['email'], FILTER_VALIDATE_EMAIL) === false) {

    $message .= "Invalid email address. <br/>";
}

if($message) {

    echo "<div class='red-error'><b>There were errors in your form:</b> <br/>" . $message . "</div>";

    } else {

    echo "<div class='green-success'>Thank you. We will respond to your enquiry as soon as possible.</div>";

    }
}

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If there are validation errors server side then it should show the error with red background, if no validation errors and form submits, then message with green background should show and I can then send email, hide the form etc.

<form id="contact-form" method="post"> <div class="col-sm-6 col-xs-12"> <label class="contact">Email Address*</label> <input type="email" name="email"> </div> <div class="col-sm-6 col-xs-12"> <label class="contact">First Name*</label> <input type="text" name="first_name"> </div> <div class="col-sm-5 col-md-4 col-xs-6"> <button id="send" type="submit" name="submit" class="btn btn--primary type--uppercase">Send Enquiry</button> </div> </form> <div id="server-results"></div>