stats-opt-in.php

<?php

add_action( 'template_redirect', 'my_stats_template_redirect_tweak', 2 );
function my_stats_template_redirect_tweak() {
	global $stats_footer;

	// If we don't have a $stats_footer global ... maybe Stats or Jetpack isn't active?
	if ( empty( $stats_footer ) ) {
		return;
	}

	// If the user has just hit a button to okay stats
	if ( ! empty( $_POST['user_okayed_stats'] ) ) {
		$time = time();
		setcookie( 'user_okayed_stats', $time, $time + YEAR_IN_SECONDS, COOKIEPATH, COOKIE_DOMAIN, false, false );
		$_COOKIE['user_okayed_stats'] = $time;
	}

	// If the user hasn't okayed stats, don't show stats, but offer a form instead:
	if ( empty( $_COOKIE['user_okayed_stats'] ) ) {
		$stats_footer = '';
		add_action( 'wp_footer', 'my_stats_opt_in_form', 99 );
	}
}

function my_stats_opt_in_form() {
	?>
	<form method="POST">
		<input type="submit" name="user_okayed_stats" value="<?php esc_attr_e( 'Opt-In to Stats Tracking!' ); ?>" />
	</form>
	<?php
}