CSS Pre-processor

css-preprocessor.php

function preprocessor($text){
	$parts = explode("~~~~~~~~~~~~~~~~", $text);
	
	$parts[0] = str_replace("\n",'',$parts[0]);
	$parts[0] = str_replace("\r",'',$parts[0]);
	
	$param = explode(";", $parts[0]);
	$style = $parts[1];
	$params = [];
		
	foreach($param as $p){
		if($p){
			$params[] = explode(" = ", $p);
		}
	}
	
	foreach($params as $p){
		if($p){
			$style = str_replace($p[0], $p[1], $style);
		}
	}
	return $style;
}

$style = file_get_contents('style.css');
$style = preprocessor($style);
echo $style;

parser.php returns

body{
	background:#000; 
	font-family: Arial; 
	letter-spacing: 1px;
	font-size:150%;
	color:#fafafa;
	cursor:default;
	margin:0px;
}

style.css

_theme_bg_color_ = #000;
_theme_text_color_ = #fafafa;

~~~~~~~~~~~~~~~~
body{
	background:_theme_bg_color_; 
	font-family: Arial; 
	letter-spacing: 1px;
	font-size:150%;
	color:_theme_text_color_;
	cursor:default;
	margin:0px;
}