A "callback" is when you execute a function, and you provide to it a name of
*another* function, which it will call on some data in the middle of its

It's a very handy way to provide extreme flexibility in functional

For example:

function my_array_walk($array, $function){
    while (list($k, $v) = each($array)){
        # Here's the magic that implements a 'callback'
        $function($k, $v);

function your_echo($key, $value){
    echo "$key $value<BR>\n";

$foo = array('a'=>1, 'b'=>2, 'c'=>3);

my_array_walk($foo, 'your_echo');

This rather silly example will "walk" the array and call 'your_echo' on each
key/value pair.

Dunno exactly how preg_ uses it though...

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----- Original Message -----
From: Arash Dejkam <[EMAIL PROTECTED]>
Newsgroups: php.general
Sent: Saturday, September 08, 2001 7:35 PM
Subject: preg_replace_callback()

> Hi,
> What is a callback in preg_replace_callback(...) ?
> how can I use it ? can anybody give me an example ?
> Thanks,
> Arash

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