function disable_00_invoices($vars) { $email_template_name = $vars['messagename']; # Email template name being sent $relid = $vars['relid']; # Related ID it's being sent for - client ID, invoice ID, etc... //Checking for certain template name, if so - this is our case if ($email_template_name == "Invoice Created" || $email_template_name == "Invoice Payment Confirmation") { //getting total of the invoice $result = select_query('tblinvoices', 'total', array("id" => $relid)); $data = mysql_fetch_assoc($result); //if it is equal to '0.00' we disable email sending if (isset($data['total']) && $data['total'] == '0.00') $merge_fields['abortsend'] = true; } return $merge_fields; } add_hook("EmailPreSend",1,"disable_00_invoices");