Placeholder/variable scope: Passing values between snippets and between docs.

Hi folks.

there is probably a simple answer to this but I can’t find anything in the wiki or forum. Please advise if this should be posted elsewhere.

I am building a multilingual site. Each doc is populated with language-specific content from a table in the MODx db, using a snippet which is called from the template: [!LanguageContent?!].
The snippet displays the language links, using [!LanguageContent? &type=`choice`!], and clicking one of these re-calls the current page but using the selected language to fetch the content from the db, using [!LanguageContent? &type=`content`!]. (ie, using the same snippet twice on the page).

The links are created as:

(I’ve simplified this by taking out some html attributes).

and end up as:


This works fine when changing language on the same page, just getting the language from $_REQUEST[’lang’] and fetching the appropriate content from the db, but it is when I want to go to another page in the menu that this system comes unstuck, as I have not added the "&do=change&lang=2" etc to the menu links (created using Wayfinder).

I tried using the value of $language_id to set a placeholder, which I could then pick up in the snippet on the next page, but the placeholder seems to expire by the time I get to the next page. Does this mean that placeholders only last as long as the current page exists and are then disposed of?

(If not, then should I be able to pick up the placeholder in Wayfinder and add the language ID to the menu links, as above?)

In summary: Is there any way of persisting a variable on the server, for the current session, which can then be used when the next browser request is made?

There are may be snippets available to do this sort of thing, which might be useful, but I would love to know exactly what happens to placeholders; how long do they last and can they be used by other snippets and between page requests?

Very much obliged if anyone can answer this for me, thanks

Yes, placeholders are stored in an array that is only good for the document being generated.

You can add a query string to links in your Wayfinder row tpl chunk. Just keep in mind that you have to use a leading ? if you’re using Friendly URLs, and a & if you’re not (the index.php?id=xx uses the leading ? in that case).

You can also use the SESSION, which is what I do. $_SESSION[’lang’] can be set and retrieved with snippets. I also like to use cookies, since the session can expire at varying intervals depending on your server configuration.

Thanks for that Susan, I like your $_SESSION suggestion, I’ll try that.

I presume that this array is available on the server to any snippet and any page for as long as the session lasts?

Is there a way to print out all of the placeholders and $_SESSION variables, so I can observe what is available at any point in time? Would print_r be the way to go?

Edit: found the answer to the above Q for $_SESSION variables - from Breezer at http://modxcms.com/forums/index.php?topic=27196.0

Cheers,

Gav

It’s a regular PHP session. http://sottwell.com/article-sessions.html

Indeed, I use this code a lot:

sometimes with a following exit(); (especially in plugins). In fact, when I’m developing, I make a function out of it that takes the variable I want to view as a parameter.

Thanks Susan,

$_SESSION works a treat! I hadn’t explored sessions in MODx before, so looking forward to seeing what I can do with this.

I do use the same 3-liner a lot myself for arrays. But what about placeholders - are they stored in an array that I can view (ie all placeholders for all snippets etc)?

Cheers,

Gav

$modx->placeholders. Keep in mind that this can vary as snippets, TVs and plugins are processed. The parser will make up to 10 passes over the document, so every pass could add to the array.

In a function, you would need to declare $modx global. To set a placeholder, it’s $modx->setPlaceholder(’name’, ’content’) and to get a placeholder it’s $modx->getPlaceholder(’name’). You can also use $modx->mergePlaceholderContent() to do the placeholder/content replacement (it actually ends up using the PHP str_replace() function). There are also a couple of API functions to set multiple placeholders using an array or an object.

Brilliant!

Thanks a lot for all that info Susan, and for your fast responses too.

Gav