Change reCAPTCHA response to alert() instead of loading new page - php

Question

I'm using reCAPTCHA and I'd like to show the response if the CATPCHA was filled in incorrectly as an alert(); rather than it loading a new page. How can I do that?
This is the form action:
<form id="form" method="POST" action="verify.php">
With this in the verify.php file:
<?php
require_once('recaptchalib.php');
$privatekey = "(my key)";
$resp = recaptcha_check_answer ($privatekey,
$_SERVER["REMOTE_ADDR"],
$_POST["recaptcha_challenge_field"],
$_POST["recaptcha_response_field"]);
if (!$resp->is_valid) {
// What happens when the CAPTCHA was entered incorrectly
die ("The reCAPTCHA wasn't entered correctly. Go back and try it again." .
"(reCAPTCHA said: " . $resp->error . ")");
} else {
// Your code here to handle a successful verification
}
?>

Answer 1

Call your method on form submit like--
<form id="form" method="POST" action="verify.php" onsubmit="mymethod()" >
OR use jquery, something like that --
<script>
$("form").submit(function() {
if ($("input:first").val() == "correct") {
$("span").text("Validated...").show();
return true;
}
$("span").text("Not valid!").show().fadeOut(1000);
return false;
});
</script>

Answer 2

You can write the Javascript for the alert on the new page.
if (!$resp->is_valid) {
// What happens when the CAPTCHA was entered incorrectly
echo("<script>alert('The reCAPTCHA wasn't entered correctly. Go back and try it again.');</script">);
die();
} else {
// Your code here to handle a successful verification
}