Tips & Tricks

Blank Variable Handling

There may be times when you want to print a default value for an empty variable instead of printing nothing, such as printing   so that html table backgrounds work properly. Many would use an {if} statement to handle this, but there is a shorthand way with Smarty, using the default variable modifier.

Note

"Undefined variable" errors will show an E_NOTICE if not disabled in PHP's error_reporting() level or Smarty's $error_reporting property and a variable had not been assigned to Smarty.

    {* the long way *}
    {if $title eq ''}
       &nbsp;
    {else}
       {$title}
    {/if}

    {* the short way *}
    {$title|default:'&nbsp;'}

See also default modifier and default variable handling.

Default Variable Handling

If a variable is used frequently throughout your templates, applying the default modifier every time it is mentioned can get a bit ugly. You can remedy this by assigning the variable its default value with the {assign} function.

{* do this somewhere at the top of your template *}
{assign var='title' value=$title|default:'no title'}

{* if $title was empty, it now contains the value "no title" when you use it *}
{$title}

See also default modifier and blank variable handling.

Passing variable title to header template

When the majority of your templates use the same headers and footers, it is common to split those out into their own templates and {include} them. But what if the header needs to have a different title, depending on what page you are coming from? You can pass the title to the header as an attribute when it is included.

mainpage.tpl - When the main page is drawn, the title of "Main Page" is passed to the header.tpl, and will subsequently be used as the title.

{include file='header.tpl' title='Main Page'}
{* template body goes here *}
{include file='footer.tpl'}

archives.tpl - When the archives page is drawn, the title will be "Archives". Notice in the archive example, we are using a variable from the archives_page.conf file instead of a hard coded variable.

{config_load file='archive_page.conf'}

{include file='header.tpl' title=#archivePageTitle#}
{* template body goes here *}
{include file='footer.tpl'}

header.tpl - Notice that "Smarty News" is printed if the $title variable is not set, using the default variable modifier.

<html>
    <head>
        <title>{$title|default:'Smarty News'}</title>
    </head>
<body>

footer.tpl

    </body>
</html>

Dates

As a rule of thumb, always pass dates to Smarty as timestamps. This allows template designers to use the date_format modifier for full control over date formatting, and also makes it easy to compare dates if necessary.

{$startDate|date_format}

This will output:

Jan 4, 2009

{$startDate|date_format:"%Y/%m/%d"}

This will output:

2009/01/04

Dates can be compared in the template by timestamps with:

{if $order_date < $invoice_date}
   ...do something..
{/if}

When using {html_select_date} in a template, the programmer will most likely want to convert the output from the form back into timestamp format. Here is a function to help you with that.

<?php

// this assumes your form elements are named
// startDate_Day, startDate_Month, startDate_Year

$startDate = makeTimeStamp($startDate_Year, $startDate_Month, $startDate_Day);

function makeTimeStamp($year='', $month='', $day='')
{
   if(empty($year)) {
       $year = strftime('%Y');
   }
   if(empty($month)) {
       $month = strftime('%m');
   }
   if(empty($day)) {
       $day = strftime('%d');
   }

   return mktime(0, 0, 0, $month, $day, $year);
}

Componentized Templates

Traditionally, programming templates into your applications goes as follows: First, you accumulate your variables within your PHP application, (maybe with database queries.) Then, you instantiate your Smarty object, assign() the variables and display() the template. So lets say for example we have a stock ticker on our template. We would collect the stock data in our application, then assign these variables in the template and display it. Now wouldn't it be nice if you could add this stock ticker to any application by merely including the template, and not worry about fetching the data up front?

You can do this by writing a custom plugin for fetching the content and assigning it to a template variable.

function.load_ticker.php - drop file in $plugins directory

<?php

// setup our function for fetching stock data
function fetch_ticker($symbol)
{
   // put logic here that fetches $ticker_info
   // from some ticker resource
   return $ticker_info;
}

function smarty_function_load_ticker($params, $smarty)
{
   // call the function
   $ticker_info = fetch_ticker($params['symbol']);

   // assign template variable
   $smarty->assign($params['assign'], $ticker_info);
}

index.tpl

{load_ticker symbol='SMARTY' assign='ticker'}

Stock Name: {$ticker.name} Stock Price: {$ticker.price}

Obfuscating E-mail Addresses

Do you ever wonder how your email address gets on so many spam mailing lists? One way spammers collect email addresses is from web pages. To help combat this problem, you can make your email address show up in scrambled javascript in the HTML source, yet it it will look and work correctly in the browser. This is done with the {mailto} plugin.

<div id="contact">Send inquiries to
{mailto address=$EmailAddress encode='javascript' subject='Hello'}
</div>

Note

This method isn\'t 100% foolproof. A spammer could conceivably program his e-mail collector to decode these values, but not likely.... hopefully..yet ... wheres that quantum computer :-?.

See also escape modifier and {mailto}.