<?php
if (isset($_POST['submit']) {
if (strlen($_POST['area']) < 50) {
die('asile rašyk daugiau');
}
}
?>
<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.10.2/jquery.min.js"></script>
<script>
$(document).ready(function () {
$('#tarea').keyup(function () {
$('#char').html($('#area').val().length);
});
});
</script>
<form method="post">
<textarea id="area" name="area"></textarea>
<input type="submit" name="submit" />
</form>
<div id="char"></div>