WP: Google +1 Button

functions.php

add_filter('the_content', 'wpr_google_plusone');
function wpr_google_plusone($content) {
	$content = $content.'<div class="plusone"><g:plusone size="tall" href="'.get_permalink().'"></g:plusone></div>';
	return $content;
}
add_action ('wp_enqueue_scripts','wpr_google_plusone_script');
function wpr_google_plusone_script() {
	wp_enqueue_script('google-plusone', 'https://apis.google.com/js/plusone.js', array(), null);
}