preg_replace after, removing /e

snippet.php

public static function decamelize($word)
{
    $callback = create_function('$matches',
        'return strtolower(strlen("$matches[1]") ? 
            "$matches[1]_$matches[2]" : "$matches[2]");');

        return preg_replace_callback(
            '/(^|[a-z])([A-Z])/',
            $callback,
            $word
        );
}