$api_key = "your API-KEY here";
wp_enqueue_script("twitter-anywhere",
	"http://platform.twitter.com/anywhere.js?id={$api_key}&v=1");
add_action("wp_head", "twitter_anywhere");

function twitter_anywhere()
{
	echo '<script type="text/javascript">';
	echo 'twttr.anywhere(onAnywhereLoad);';
	echo 'function onAnywhereLoad(twitter) { twitter.hovercards(); }';
	echo '</script>';
}

enable hovercards in functions.php

wordpress

PHP