Using links in frontend plugins

$content = '<a href="index.php?id='.$GLOBALS['TSFE']->id.

    '&doTheMagic=1">Do it!</a>';

$content = '<a href="index.php?id='.$GLOBALS['TSFE']->id.

    '&L=' . intval (t3lib_div::_GP('L')).

    '&doTheMagic=1">Do it!</a>';

Let's start with the easy ones. I'll just give you an example for each of the first three functions. Note that these are very simplistic, non real-world examples and not all parameters of the pi_base methods are discussed here. Again: Have a look into the sources, all the parameters are explained there.

pi_getPageLink: 

   1:     // Link to the parent page and if there is none, link to

    // the current page instead:

   3:if (intval($GLOBALS['TSFE']->page['pid'])) {

   4:     $label = 'parent page';

   5:     $id = $GLOBALS['TSFE']->page['pid'];

} else {

   7:     $label = 'this page';

   8:     $id = $GLOBALS['TSFE']->id;

}

  11:     // Create the link and a sample form:

  12:$link = $this->pi_getPageLink($id)

  13:$out = '

  14:     <form action="'.$link.'">

  15:         <input type="submit" value="' . $label . '" />

    </form>

  17: ';

pi_linkToPage: 

   1:     // Prepare the trick:

   2:$label = 'Do the magic on a different page';

   3:$id = 43; // The magic page

   4:$params = array (

   5:     'doTheMagic' => 1

   6:);

   7:     // Create the link:

   8:$out = $this->pi_linkToPage($label, $id, '', $params);

pi_linkTP: 

1:     // Get prepared:

   2:$counter = intval (t3lib_div::_GP('tx_myext_counter'));

   3:$label = 'Increase by 1';

   4:$params = array (

   5:     'tx_myext_counter' => $counter + 1,

   6:     'tx_myext_mood' => t3lib_div::_GP('tx_myext_mood'),

);

   8:     // Create the link:

   9:$out = 'The current value is ' . $counter;

$out .= $this->pi_linkTP ($label, $params)

Side note: In some examples I used the function t3lib_div::_GP() which returns GET and POST variables. If you don't know about the class t3lib_div yet, have a look at it's file in the t3lib/ directory. It contains a great collection of useful functions which make a TYPO3 coder's day easier.

While these three functions are quite self-explanatory, the remaining two need further examination (I'll skip pi_list_linkSingle which belongs to the list view / single view functions pibase). They do something with the so called piVars, but what are piVars then?

As you have seen in the last example (pi_linkTP), a GET (or POST) variable called tx_myext_mood has been added to the URL parameters although we didn't touch it. This variable might be passed to our script from somewhere else and we now have to take care that we don't lose it while we're linking to our own page.

But why do we have to take care of tx_myext_mood while the type parameter is handled automatically? Well, that is because some parameters might be registered with the linkVars TypoScript directive (see <link http: typo3.org documentation document-library core-documentation doc_core_tsref current>TSref for details) and tx_myext_mood obviously isn't.

Wouldn't it be great if we could register a certain set of parameters (ie. variables) which we use in our extension and they are passed to our script each time we link to it? That's what the piVars are for.

piVars

Actually piVars is only an array in the pi_base class which we can use in our frontend plugin (because it is inherited from pi_base). Let's fill it with some important information:

$this->piVars['mood'] = 'great';

$this->piVars['boardingSkillLevel'] = 'neverSeenSnow';

Now, if you use the link functions with ...keepPIvars in their name, you won't have to take care of these values – they are just passed with each link you create:

$out = pi_linkTP_keepPIvars ('link to myself');

will generate a link like this:

<a href="index.php?id=3&tx_myext[mood]=great&tx_myext[boardingSkillLevel]=neverSeenSnow">link to myself</a>

... and if you changed your mood in the meantime, just modify the parameter:

$out = pi_linkTP_keepPIvars ('link to myself',

array ('mood'=>'overwhelmed', 'boardingSkillLevel' => null));

<a href="index.php?id=3&tx_myext[mood]=overwhelmed>link to myself</a>

Play around with this concept and especially have a look at the sample code the kickstarter wizard creates for you.