Get reliable byte length of a string in PHP. Works around an issue where the multibyte string extension can be configured to shadow strlen().

string-bytelen.php

<?php
/**
 * Works around an issue where the multibyte string extension
 * can be configured to shadow strlen(), and no longer returns pure
 * bytelength.
 * @param  string $str string to get byte length of
 * @return int
 */
function bytelen($str)
{
	static $has_mbstring = extension_loaded('mbstring');
	static $has_mb_shadow = (int) ini_get('mbstring.func_overload');

	if ($has_mbstring && ($has_mb_shadow & 2)) {
		return mb_strlen($str, 'latin1');
	} else {
		return strlen($str);
	}
}