Best way to implement conditional in a PHP templating system?

Question

I'm creating a very simple PHP templating system for a custom CMS/news system. Each article has the intro and the full content (if applicable). I want to have a conditional of the form:

{continue}click to continue{/continue}

So if it's possible to continue, the text "click to continue" will display, otherwise, don't display this whole string. So far, it works like this: if we can continue, remove the {continue} tags; otherwise, remove the whole thing.

I'm currently using preg_match_all to match the string in the second case. What is the best function for removing the matched text? A simple str_replace, or something else?

Or is there a better way to implement this overall?

Answer 1

Why not use preg_replace_callback?

Specifically:

preg_replace_callback('!\{continue\}(.*)\{/continue\}!Us', 'replace_continue', $html);

function replace_continue($matches) {
  if (/* can continue */) {
    return $matches[1];
  } else {
    return '';
  }
}

I find preg_replace_callback to be incredibly useful.

Answer 2

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Answer 3

For PHP templating systems the proper way is to parse the template (using state machine or at least preg_split), generate PHP code from it, and then use that PHP code only. Then you'll be able to use normal if for conditional expressions.

Regular expressions aren't good idea for implementing templates. It will be PITA to handle nesting and enforce proper syntax beyond basic cases. Performance will be very poor (you have to be careful not to create backtracking expression and even then you'll end up scanning and copyng KBs of templates serveral times).