<textarea id="area" cols="70" rows="30"></textarea>
<button id="submit">Submit</button>

<script>
    $('#submit').click(function (e) {
        e.preventDefault();

        var info = $('#area').val();

        $.ajax({
            type: "POST",
            url: 'pages/assignments/response.php',
            data: {area: info},
            success: function (response) {
                console.log(response);
            }
        });
    });
</script>

<?php
if (!empty($_POST['area'])) {
    runEval($_POST['area']);
};

function runEval($data)
{
//    $data = preg_replace('/s+/', '', $data); doesn't seem to work at all with it)
    $characters = '[a-zA-Z0-9]*';
    $functions = '';
    $operators = '[w-><$(){}|_+=":;!&*%$]';
    $regexp = '/^((' . $characters . '|' . $functions . 's*((?1)+)|((?1)+))(?:' . $operators . '(?2))?)+/'; /*honestly we have no idea what it does, because we copied it and changed the $characters,$functions,$operators*/

    if (preg_match($regexp, $data)) {
        eval('$result = ' . $data . ';');
        echo $result;
    } else {
        $data = false;
    }
}

?>