[Vince]

PHP код:

ToLowerExtended(string[], len = sizeof string)
{
    for(new i; i < len; i++)
    {
        // basic Latin
        if('A' <= string[i] <= 'Z')
        {
            string[i] += 0x0020;
            continue;
        }
        
        // Latin-1 Supplement
        if((0x00C0 <= string[i] <= 0x00DE) && string[i] != 0x00D7) // 00D7 is multiplication symbol
        {
            string[i] += 0x0020;
            continue;
        }
        
        // Latin Extended-A
        if((0x0100 <= string[i] <= 0x017F) && !(string[i] & 1)) // even numbers are uppercase
        {
            string[i] += 0x0001;
            continue;
        }    
    }
} 


Not tested, based off of http://unicode-table.com