Sorcellerie Web

function parseHttpAcceptLanguage($str=NULL) {
        // getting http instruction if not provided
        $str=$str?$str:$_SERVER['HTTP_ACCEPT_LANGUAGE'];
        // exploding accepted languages 
        $langs=explode(',',$str);
        // creating output list
        $accepted=array();
        foreach ($langs as $lang) {
                // parsing language preference instructions
                // 2_digit_code[-longer_code][;q=coefficient]
                ereg('([a-z]{1,2})(-([a-z0-9]+))?(;q=([0-9\.]+))?',$lang,$found);
                // 2 digit lang code
                $code=$found[1];
                // lang code complement
                $morecode=$found[3];
                // full lang code
                $fullcode=$morecode?$code.'-'.$morecode:$code;
                // coefficient
                $coef=sprintf('%3.1f',$found[5]?$found[5]:'1');
                // for sorting by coefficient
                $key=$coef.'-'.$code;
                // adding 
                $accepted[$key]=array('code'=>$code,'coef'=>$coef,'morecode'=>$morecode,'fullcode'=>$fullcode);
        }
        // sorting the list by coefficient desc
        krsort($accepted);
        return $accepted;
}

This function will parse a given HTTP Accepted language instruction (or retrieve it from $_SERVER if not provided) and will return a sorted array. For example, it will parse fr;en-us;q=0.8 to :

The next thing will be to find and serve the first available version amongst user's accepted languages. Easy.