Online PHP editor | refs for CT5A6

<?php function camelCaseToUnderscore($input) { return strtolower(preg_replace('/(?<!^)[A-Z]([A-Z](?![a-z]))*/', '_$0', $input)); } echo camelCaseToUnderscore('CamelCaseForTheWin'), "\n"; echo camelCaseToUnderscore('ACar'), "\n"; echo camelCaseToUnderscore('BuyACar'), "\n"; echo camelCaseToUnderscore('XML'), "\n"; echo camelCaseToUnderscore('SimpleXML'), "\n";