How can I use strlen in php for Persian?

I have this code:

$string = 'علی';
echo strlen($string);

Since $string has 3 Persian characters, output must be 3 but I get 6.

علی has 3 characters. Why my output is 6 ?

How can I use strlen() in php for Persian with real output?

Answer

try this:

function ustrlen($text)
{
    if(function_exists('mb_strlen'))
        return mb_strlen( $text , 'utf-8' );
    return count(preg_split('//u', $text)) - 2;
}

it will work for any php version.