Extract Information from post content (using regex?)

This belongs to stackoverflow. Here’s a solution anyway:

$content = preg_replace_callback('/\%replaceContent:{(.*?)}\%/', 'do_replacements', $content);

function do_replacements($matches){

  $type = $matches[1]; // here's your {type}
  $replacement = "...replacement for {$type}";  

  return $replacement; 
}