The setup for my templating system:

$template=array(
  "/({PAGETOP})/",
  "/({PAGENAVBAR})/",
  "/({PAGEMAIN})/",
  "/({PAGELINKS})/",
  "/({PAGESPACE})/",
  "/({PAGETEXT})/",
  "/({PAGENEWS})/",
  "/({PAGEBOTTOM})/",
  "/({PAGEDATA})/"
  );

$pagevars=array(
  "PAGETOP" => get_page($site->page_top),
  "PAGENAVBAR" => get_page($site->page_top),
  "PAGEMAIN" => get_page($site->page_main),
  "PAGELINKS" => get_page($site->page_links),,
  "PAGESPACE" => get_page($site->page_space),
  "PAGETEXT" => get_page($site->page_text),
  "PAGENEWS" => get_page($site->page_news),,
  "PAGEBOTTOM" => get_page($site->page_bottom),
  "PAGEDATA" => ""
  );

$page = "{PAGETOP}{PAGENAVBAR}{PAGEMAIN}{PAGEBOTTOM}";

$page = preg_replace($template,$pagevars,$page);

echo $page;

Basically each physical page referenced via the get_page function is a text template that may contain HTML, text or variables in the form {VAR}.

Eventually content from a database ends up in a variable called PAGEDATA which is in the template stored in the page main variable.

The problem:

PAGEDATA ends up containing page text and it has something like "would cost around $16,000 to complete" in that text.

When the preg_replace is performed, something somewhere is assuming that $16 is a variable (which doesn't exist) and the text ends up as "would cost around ,000 to complete"