<?php
echo preg_replace_callback('~[A-Z]~', function($_) { return chr(32 + ord($_[0])); }, 'Important: you are NOT allowed to use a built-in function that converts the string (or just one character) to lowercase (such as ToLower() in .NET, strtolower() in PHP , ...)! You\'re allowed to use all other built-in functions, however.');
important: you are not allowed to use a built-in function that converts the string (or just one character) to lowercase (such as tolower() in .net, strtolower() in php , ...)! you're allowed to use all other built-in functions, however.