display sequence of days

function weekendDaysToString($days, $lang = 'en') {
    $and = array('pt'=>'e', 'en'=>'and');
    $strWeek = array(     // config with more langs!
        'pt'=>array("Segunda", "Terça", "Quarta", "Quinta", "Sexta",
            "Sábado", "Domingo"),
        'en'=> array("Monday", "Tuesday", "Wednesday", "Thursday",
            "Friday", "Saturday", "Sunday")
    );
    $days = array_unique($days);
    sort($days);
    $seq = preg_replace_callback(  // Split sequence by ",":
        '/0246|024|025|026|135|146|246|02|03|04|05|06|13|14|15|16|24|25|26|35|36|46/',
        function ($m) { return join( ',' , str_split($m[0]) ); },
        implode('',$days)
    );
    // split two or more days by "-":
    $seq = preg_replace('/(\d)\d*(\d)/', '$1-$2', $seq);
    $a = explode(',',$seq);
    $last = array_pop($a);
    $n = count($a);
    // Formatting and translating:
    $seq = $n? implode(", ",$a): $last;
    if ($last && $n) $seq = "$seq $and[$lang] $last";
    return preg_replace_callback(
        '/\d/',
        static function ($m) use (&$strWeek,$lang) {
            return $strWeek[$lang][$m[0]];
        },
        $seq
    );
}



############## TESTINGS #################
print "\n".weekNumbers_toStr(array(6,1,2,3,6),'en'); // corrects order and dups
print "\n".weekNumbers_toStr(array(0,1,2,3,6));      // Monday-Thursday and Sunday

print "\n".weekNumbers_toStr(array(3,4,6),'pt');  // Quinta-Sexta e Domingo
print "\n".weekNumbers_toStr(array(3,4,6));       // Thursday-Friday and Sunday

print "\n".weekNumbers_toStr(array(2,3,4,6));  // Wednesday-Friday and Sunday
print "\n".weekNumbers_toStr(array(3,5));      // Thursday and Saturday
print "\n".weekNumbers_toStr(array(0,2,4,6));  // Monday, Wednesday, Friday and Sunday
print "\n".weekNumbers_toStr(array(0));        // Monday
print "\n".weekNumbers_toStr(array());