Why will a regex pattern with leading and trailing .* only make one replacement?

Question

I'm developing a simple template engine and trying to implement my own simple syntax for handling loops and eventually if statements rather than including PHP in my template files.

I know a lot of people will say don't bother or just use an existing system, but as it's for my dissertation I want as much of it to be my own work as possible!

Anyway, back to the problem. I've got the following code in a my template file as an example:

<p>Template Header</p>
{{foreach{array1}}}
    <p>This is the first content line that should be displayed.</p>
{{/foreach}}
{{foreach{array2}}}
    <p>This is the second content line that should be displayed.</p>
{{/foreach}}
<p>Template Footer</p>

I've then got the following PHP to read the file, look for loops and extract them.

<?php
$template = file_get_contents('reg.html');
$expression = "#.*{{foreach{(.*?)}}}(.*?){{/foreach}}.*#is";
$result = preg_replace($expression, "$1", $template);  
var_dump($result);
?>

When calling preg_replace() and dumping the result $1 is giving me the array name which will be used for the loop (array1 or array2), then changing it to $2 will give me the content between the loop tags. Perfect. The problem is it only works for one {{foreach}} tag.

Is there anyway I can loop all matches of the regex to get the results I'm getting above?

Answer 1

$expression = "#.*{{foreach{(.*?)}}}(.*?){{/foreach}}.*#is";
                ^^                                   ^^

You are not just matching the "foreach" template tag, but also everything before and after it. That means the second foreach will get eaten up by .* too. So you can't match it again.