Change admin_change email tempalte sent by Paid Memberships Pro to members when they move from one level to another. Useful for "approval" workflows on sign up.

my_pmpro_email_filter.php

/*
  Change admin_change email sent to members when they move from "Applicant" level to "Approved" level.
  You should have two levels, "Applicant" level ID 1 and "Approved" level ID 2.
  If the names or IDs of your levels are different, you will have to change the code below.
  You also need a file "applicant_approved.html" in the ../themes/yourtheme/paid-memberships-pro/email/ directory.
*/
function my_pmpro_email_filter($email)
{	
	if($email->template == "admin_change" && $email->data['membership_level_name'] == "Approved")
	{
		//check if this user's last level was 1
		global $wpdb;
		$user = get_user_by("login", $email->data['user_login']);
		$last_level_id = $wpdb->get_var("SELECT membership_id FROM $wpdb->pmpro_memberships_users WHERE user_id = '" . $user->ID . "' AND status != 'active' ORDER BY id DESC LIMIT 1"); 		
		if($last_level_id != 1)
			return $email;			//wasn't an applicant before this change.
		
		//update subject
		$email->subject = "Your application to " . get_option('blogname') . " has been approved.";

		//update body
		$email->body = file_get_contents(get_stylesheet_directory() . "/paid-memberships-pro/email/applicant_approved.html");

		//replace data
		if(is_string($email->data))
			$email->data = array("body"=>$data);
		if(is_array($email->data))
		{
			foreach($email->data as $key => $value)
			{
				$email->body = str_replace("!!" . $key . "!!", $value, $email->body);
			}
		}
	}
	
	return $email;
}
add_filter("pmpro_email_filter", "my_pmpro_email_filter");