Check to see if a string is UTF-8 and convert it if it's not. Accidentally posted this as anonymous before :(

convert_to_utf8.php

<?php
function getUtf8String($string) {
    if ( !isUtf8($string) )
		return utf8_encode($string);
	return $string;
}

function isUtf8($string) {
	if ( function_exists("mb_check_encoding") ) {
		return mb_check_encoding($string, 'UTF8');
	}

	return preg_match('%^(?:
			[\x09\x0A\x0D\x20-\x7E]            # ASCII
			| [\xC2-\xDF][\x80-\xBF]             # non-overlong 2-byte
			|  \xE0[\xA0-\xBF][\x80-\xBF]        # excluding overlongs
			| [\xE1-\xEC\xEE\xEF][\x80-\xBF]{2}  # straight 3-byte
			|  \xED[\x80-\x9F][\x80-\xBF]        # excluding surrogates
			|  \xF0[\x90-\xBF][\x80-\xBF]{2}     # planes 1-3
			| [\xF1-\xF3][\x80-\xBF]{3}          # planes 4-15
			|  \xF4[\x80-\x8F][\x80-\xBF]{2}     # plane 16
	)*$%xs', $string);
}