PHP - Counts the number of bytes in a string, regardless of any mbstring overloading.

count_bytes.php

// Counts the number of bytes in a string.
function count_bytes( &$str ) {
    if( ini_get( 'mbstring.func_overload' ) ) {
        return mb_strlen( $str, '8bit' );
    }
    // Ideally we want strlen() to be used, because it's fast.
    return strlen( $str );
}