短网址服务，可能很多朋友都已经不再陌生，现在大部分微博、手机邮件提醒等地方已经有很多应用模式了，并占据了一定的市场。估计很多朋友现在也正在使用。 看过新浪的短连接服务，发现后面主要有6个字符串组成。
太多算法的东西，也没必要去探讨太多，最主要的还是实现，下面是三种方法的代码：
//纯随机生成方法
function random($length,$pool = '')
{
$random = '';
if (empty($pool)) {
$pool = 'abcdefghkmnpqrstuvwxyz';
$pool .= '23456789';
}
srand ((double)microtime()*1000000);
for($i = 0; $i < $length; $i++)
{
$random .= substr($pool,(rand()%(strlen ($pool))),1);
}
return $random; }
$a=random(6);
print_r($a);
// 枚举生成方法
function shorturl($input) {
$base32 = array (
"0","1","2","3","4","5","6","7","8","9","a","b","c","d","e","f","g","h","i","j","k","l","m","n","o","p","q","r","s","t","u","v","w","x","y","z","A","B","C","D","E","F","G","H","I","J","K","L","M","N","O","P","Q","R","S","T","U","V","W","X","Y","Z"
);
$hex = md5($input);
$hexLen = strlen($hex);
$subHexLen = $hexLen / 8;
$output = array();
for ($i = 0; $i < $subHexLen; $i++) {
$subHex = substr ($hex,$i 8,8);
$int = 0x3FFFFFFF & (1 ('0x'.$subHex));
$out = '';
for ($j = 0; $j < 6; $j++) {
$val = 0x0000001F & $int;
$out .= $base32[$val];
$int = $int >> 5;
}
$output[] = $out;
}
return $output;
}
$a=shorturl("//www.jb51.cc");
print_r($a);
//62 位生成方法
function base62($x)
{
$show= '';
while($x> 0) {
$s= $x% 62;
if($s> 35) {
$s= chr($s+61);
} elseif($s> 9 && $s<=35) {
$s= chr($s+ 55);
}
$show.= $s;
$x= floor($x/62);
}
return $show;
}
function urlShort($url)
{
$url= crc32($url);
$result= sprintf("%u",$url);
return base62($result);
}
echo urlShort("//www.jb51.cc/");
?>
