Using reCAPTCHA with WP Job Manager

gistfile1.php

<?php
// Define your keys here
define( 'RECAPTCHA_SITE_KEY', 'XXX' );
define( 'RECAPTCHA_SECRET_KEY', 'XXX' );

// Enqueue Google reCAPTCHA scripts
add_action( 'wp_enqueue_scripts', 'recaptcha_scripts' );

function recaptcha_scripts() {
	wp_enqueue_script( 'recaptcha', 'https://www.google.com/recaptcha/api.js' );
}

// Add reCAPTCHA to the job submission form
add_action( 'submit_job_form_company_fields_end', 'recaptcha_field' );

function recaptcha_field() {
	?>
	<fieldset>
		<label>Are you human?</label>
		<div class="field">
			<div class="g-recaptcha" data-sitekey="<?php echo RECAPTCHA_SITE_KEY; ?>"></div>
		</div>
	</fieldset>
	<?php
}

// Validate
add_filter( 'submit_job_form_validate_fields', 'validate_recaptcha_field' );

function validate_recaptcha_field( $success ) {
	$response = wp_remote_get( add_query_arg( array(
		'secret'   => RECAPTCHA_SECRET_KEY,
		'response' => isset( $_POST['g-recaptcha-response'] ) ? $_POST['g-recaptcha-response'] : '',
		'remoteip' => isset( $_SERVER['HTTP_X_FORWARDED_FOR'] ) ? $_SERVER['HTTP_X_FORWARDED_FOR'] : $_SERVER['REMOTE_ADDR']
	), 'https://www.google.com/recaptcha/api/siteverify' ) );

	if ( is_wp_error( $response ) || empty( $response['body'] ) || ! ( $json = json_decode( $response['body'] ) ) || ! $json->success ) {
		return new WP_Error( 'validation-error', '"Are you human" check failed. Please try again.' );
	}

	return $success;
}