十进制到62进制的转换

function dec2s2($num){
    $base='0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';
    $result='';
    while($num!=0){
        $result=$base[$num%62].$result;
        $num=intval($num/62);
    }
    return $result;
}

function s22hex($num){
    $base=array(
        '0'=>0,'1'=>1,'2'=>2,'3'=>3,'4'=>4,'5'=>5,'6'=>6,'7'=>7,'8'=>8,'9'=>9,
        'a'=>10,'b'=>11,'c'=>12,'d'=>13,'e'=>14,'f'=>15,'g'=>16,'h'=>17,'i'=>18,
        'j'=>19,'k'=>20,'l'=>21,'m'=>22,'n'=>23,'o'=>24,'p'=>25,'q'=>26,'r'=>27,
        's'=>28,'t'=>29,'u'=>30,'v'=>31,'w'=>32,'x'=>33,'y'=>34,'z'=>35,'A'=>36,
        'B'=>37,'C'=>38,'D'=>39,'E'=>40,'F'=>41,'G'=>42,'H'=>43,'I'=>44,'J'=>45,
        'K'=>46,'L'=>47,'M'=>48,'N'=>49,'O'=>50,'P'=>51,'Q'=>52,'R'=>53,'S'=>54,
        'T'=>55,'U'=>56,'V'=>57,'W'=>58,'X'=>59,'Y'=>60,'Z'=>61
    );
    $result=0;
    for($i=0,$len=strlen($num);$i<$len;$i++){
        $result=$result*62+$base[$num[$i]];
    }
    return $result;
}