Using css variables with php in joomla 3 template - php

Question

My idea is to use template parameter in joomla to set the color for a background, text or buttons.
I want to define a css class instead of each time using style="background-color:<?php echo $buttoncolor ?>;" as I don't want to write countless template overrides.
I believe that could be very usefull feature.
The parameter in my templateDetails.xml looks like
<field name="buttoncolor" type="color" default="#309000"
label="TPL_BUTTON_COLOR_LABEL"
description="TPL_BUTTON_COLOR_DESC" />
The idea how to use php variable in css I found on CSS-Tricks
To use a php variable within a css I linked to this file in my index.php
<link rel="stylesheet" href="<?php echo $this->baseurl ?>/templates/<?php echo $this->template; ?>/css/style.php" type="text/css" />
My style.php looks like:
<?php
header("Content-type: text/css; charset: UTF-8");
$buttoncolor = $this->params->get("buttoncolor");
?>
.buttoncolor {background-color: <?php echo $this->params->get('buttoncolor'); ?>;}
Usally I set a variable to a template parameter in the index.php like
<?php
//parameter
$app = JFactory::getApplication();
$doc = JFactory::getDocument();
$params = $app->getParams();
$buttoncolor = $this->params->get('buttoncolor');
?>
Unfortunately I got the following error:
Fatal error: Using $this when not in object context in style.php
Any ideas, workaround and help is highly appreciated!

Answer 1

Please try to remove $this. Your code has to be:
$app = JFactory::getApplication();
$template = $app->getTemplate(true);
$params = $template->params;
$buttoncolor = $params->get("buttoncolor");
Joomla has a specific way to set css style. You have to do it like:
$document = JFactory::getDocument();
$style = ".buttoncolor {background-color: ".$buttoncolor."}";
$document->addStyleDeclaration($style);
Good Luck!