replacing variables in output in php

Right now I have this code.

<?php
    error_reporting(E_ALL);

    require_once('content_config.php');

    function callback($buffer)
    {
        // replace all the apples with oranges
        foreach ($config as $key => $value)
        {
            $buffer = str_replace($key, $value, $buffer);
        }
        return $buffer;
    }

    ob_start("callback");
?>
some content
<?php

ob_end_flush();

?>

in the content_config.php file:

$config['SiteName'] = 'MySiteNa开发者_如何学Pythonme';
$config['SiteAuthor'] = 'thatGuy';

What I want to do is that I want to replace the placeholders that with the key of the config array with its value.

Right now, it doesn't work :(

your callback function cant see $config. you must either pass it as an argument or declare it global

global $config;

http://php.net/manual/en/language.variables.scope.php

as an aside you can use arrays with str_replace

$buffer = str_replace(array_keys($config), array_values($config), $buffer);

this avoids a loop, which is always good.