Weibo short link algorithm PHP version_PHP tutorial

1) Generate a 32-bit signature string from the long URL md5, divided into 4 segments, each segment is 8 bytes;

2) For these four segments of loop processing, take 8 bytes, treat them as hexadecimal strings and operate with 0x3fffffff (30 bits 1), that is, ignore processing exceeding 30 bits;

3) These 30 digits are divided into 6 segments. Each 5-digit number is used as an index of the alphabet to obtain a specific character, and the 6-digit string is obtained in sequence;

4) The total md5 string can obtain four 6-digit strings; any one of them can be used as the short URL address of this long URL;

Below is the PHPcode:

function shorturl($url='', $prefix='', $suffix='') {

$base32 = array (

'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', '0', '1', '2', '3', '4', '5');

$hex = md5($prefix.$url.$suffix);

$hexLen = strlen($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;

}

$urls = shorturl('http://www.php100.com');