PHP regex templating - find all occurrences of {{var}} - php

Question

I need some help with creating a regex for my php script. Basically, I have an associative array containing my data, and I want to use preg_replace to replace some place-holders with real data. The input would be something like this:
<td>{{address}}</td><td>{{fixDate}}</td><td>{{measureDate}}</td><td>{{builder}}</td>
I don't want to use str_replace, because the array may hold many more items than I need.
If I understand correctly, preg_replace is able to take the text that it finds from the regex, and replace it with the value of that key in the array, e.g.
<td>{{address}}</td>
get replaced with the value of $replace['address']. Is this true, or did I misread the php docs?
If it is true, could someone please help show me a regex that will parse this for me (would appreciate it if you also explain how it works, since I am not very good with regexes yet).
Many thanks.

Answer 1

Use preg_replace_callback(). It's incredibly useful for this kind of thing.
$replace_values = array(
'test' => 'test two',
);
$result = preg_replace_callback('!\{\{(\w+)\}\}!', 'replace_value', $input);
function replace_value($matches) {
global $replace_values;
return $replace_values[$matches[1]];
}
Basically this says find all occurrences of {{...}} containing word characters and replace that value with the value from a lookup table (being the global $replace_values).

Answer 2

For well-formed HTML/XML parsing, consider using the Document Object Model (DOM) in conjunction with XPath. It's much more fun to use than regexes for that sort of thing.

Answer 3

To not have to use global variables and gracefully handle missing keys you can use
function render($template, $vars) {
return \preg_replace_callback("!{{\s*(?P<key>[a-zA-Z0-9_-]+?)\s*}}!", function($match) use($vars){
return isset($vars[$match["key"]]) ? $vars[$match["key"]] : $match[0];
}, $template);
}