Hook a PHP existing function to trigger a function when called - php

Question

For MVC reasons, I want to be able to trigger a function to find when the function has been called, since Codeigniter has functions around their core, I want to hook a function such as setcookie and create a file when it's been called (from the triggered function) for example:
function call_me()
{
$file = fopen('setcookie.txt', 'a+');
fwrite($file, 'Called at ' . __CLASS__);
fclose();
}
So when setcookie is called, it should trigger the call_me function. Is there any specific function or method to do this? I know about debug_backtrace but that's not the purpose I want.

Answer 1

What you basically need to have a look at is Observers.
The observer pattern (aka. Dependents, publish/subscribe) is a
software design pattern in which an object, called the subject,
maintains a list of its dependents, called observers, and notifies
them automatically of any state changes, usually by calling one of
their methods. It is mainly used to implement distributed event
handling systems. Observer is also a key part in the familiar MVC
architectural pattern. In fact the observer pattern was first
implemented in Smalltalk's MVC based user interface framework.1
Why don't you try what is described here :
http://devzone.zend.com/1384/observer-pattern-in-php/

Answer 2

I know about debug_backtrace but that's not the purpose I want.
I see that you insist not to use backtrack function, but still I believe that when you want to log when a function is called backtrack can come in handy.
The idea is that you have a predifined piece pf code stored in a constant, whenever you want to debug an if condition evaluates this code.
If you are under prouction the if statement will prevent from evaluating anything so your code's speed is not affected. If it works for you you can modify it to your needs, to track down even more levels.
To make my point this is a full example, if I have not understood right and this is not what you're looking for, my apologies!
To check the example you have a file: test.php
<?php
define ('__SITE_PATH',realpath(dirname(__FILE__)).'/');
ini_set('log_errors', 1);
ini_set('error_log', __SITE_PATH.'my_error_log.log');
include 'test1.php';
include 'test2.php';
define (__DEBUG_EVAL, '
$dbt = debug_backtrace();
error_log(
"\n".
"Parent function file: " . $dbt[1]["file"] . "\n" .
"Parent function class: " . $dbt[2]["class"] . "\n" .
"Parent fiunction name: " . $dbt[2]["function"] . "\n" .
"Par. fiunc. called from line: " . $dbt[2]["line"] . "\n" .
"Child function file: " . $dbt[0]["file"] . "\n" .
"Child function class: " . $dbt[1]["class"] . "\n" .
"Child fiunction name: " . $dbt[1]["function"] . "\n" .
"Child fiunc. called from line: " . $dbt[1]["line"] . "\n" .
"\n"
);
');
test1::a();
?>
This is test1.php
<?PHP
class test1
{
public static function a()
{
test2::b();
}
}
?>
The last is test2.php
<?PHP
class test2
{
public static function b()
{
if(defined('__DEBUG_EVAL')) eval(__DEBUG_EVAL);
echo 'Hello!';
}
}
?>
This is the result:
[13-Apr-2012 14:37:18]
Parent function file: C:\PHP-GTK\MyProjects\Electre\test1.php
Parent function class: test1
Parent fiunction name: a
Par. fiunc. called from line: 29
Child function file: C:\PHP-GTK\MyProjects\Electre\test2.php
Child function class: test2
Child fiunction name: b
Child fiunc. called from line: 7