[solved] transform html bofore output

[Terion]

SOLVED by using a HOOK parseFrontendTemplate.
Thank you, everybody

I need to replace some contents on every page before output it.
At first look it's not a problem.
Opening index.php, adding a line:

$strBuffer = str_replace("a", "b", $strBuffer);

before

echo $strBuffer;

And.... And nothing :shock:

How can i do this?

More shock I've had, when I commented out echo $strBuffer; and page loaded.
Moreover, I've tried to change Copyright notice section (preg_replace) (to see the effect only) — and nothing changed :shock:
Mistery..

Caching is disabled...

[Tru]

Why not use a HOOK?

[Terion]

Hm, Thank you, I'll try.
The outputFrontendTemplate hook is suitable here?

[Terion]

I can't understand how to implement hooks
I am trying to extend Contao's functions at the first time and don't clearly understand, how.
I've added this:

$GLOBALS['TL_HOOKS']['outputFrontendTemplate'][] = array('myoutput', 'myfunc');

Directly into index.php
Then I've made a file myoutput.php in the root of the site, placed there:

<?php
public function myfunc($strContent, $strTemplate)
{
$strContent = str_replace("a", "b", $strContent);
return $strContent;
}
?>

and got error

Fatal error: Could not load class changetags in .../system/functions.php on line 76

Where should I put the file?
Or I'm doing everything wrong?

[Tru]

You must define the HOOK within a module. Take a look at /system/modules/news/config/config.php (there you define a hook) and /system/modules/news/News.php (the function). Then create your own files.

[Terion]

I've tried to add the hook..
Because I need just one single transform with no backend/frontend modules, I've added it into News module...

$GLOBALS['TL_HOOKS']['outputFrontendTemplate'][] = array('changetags', 'htmlchange');

And in changetags.php put the function, like mentioned here.
But I've got an error: Parse error: syntax error, unexpected T_PUBLIC in /.../system/modules/news/changetags.php on line 2
Line 2 is:

public function htmlchange($strContent, $strTemplate) {

I realy don't understand, what is the error? O_O