Classic PHP encryption and decryption function Authcode () fixed version code _ PHP

This article mainly introduces the fixed version code of the classic PHP encryption and decryption function Authcode (). If you need it, you can refer to the Authcode function, which is used by many people. this function comes from the Discuz program, used to encrypt and decrypt strings. you can set the key and Expiration Time, which is often used. The original function code may generate characters such as +,/, and &. as a result, the function code is escaped when the value is retrieved through the URL and cannot be decrypted. The network on the fire end is slightly modified. replace these characters with other characters, and then replace them with each other during decryption. this is perfect!

The code is as follows:

function authcode($string, $operation = 'DECODE', $key = '', $expiry = 0){  if($operation == 'DECODE') { $string = str_replace('[a]','+',$string); $string = str_replace('[b]','&',$string); $string = str_replace('[c]','/',$string); } $ckey_length = 4; $key = md5($key ? $key : 'livcmsencryption '); $keya = md5(substr($key, 0, 16)); $keyb = md5(substr($key, 16, 16)); $keyc = $ckey_length ? ($operation == 'DECODE' ? substr($string, 0, $ckey_length): substr(md5(microtime()), -$ckey_length)) : ''; $cryptkey = $keya.md5($keya.$keyc); $key_length = strlen($cryptkey); $string = $operation == 'DECODE' ? base64_decode(substr($string, $ckey_length)) : sprintf('%010d', $expiry ? $expiry + time() : 0).substr(md5($string.$keyb), 0, 16).$string; $string_length = strlen($string); $result = ''; $box = range(0, 255); $rndkey = array(); for($i = 0; $i <= 255; $i++) {  $rndkey[$i] = ord($cryptkey[$i % $key_length]); } for($j = $i = 0; $i < 256; $i++) {  $j = ($j + $box[$i] + $rndkey[$i]) % 256;  $tmp = $box[$i];  $box[$i] = $box[$j];  $box[$j] = $tmp; } for($a = $j = $i = 0; $i < $string_length; $i++) {  $a = ($a + 1) % 256;  $j = ($j + $box[$a]) % 256;  $tmp = $box[$a];  $box[$a] = $box[$j];  $box[$j] = $tmp;  $result .= chr(ord($string[$i]) ^ ($box[($box[$a] + $box[$j]) % 256])); } if($operation == 'DECODE') {  if((substr($result, 0, 10) == 0 || substr($result, 0, 10) - time() > 0) && substr($result, 10, 16) == substr(md5(substr($result, 26).$keyb), 0, 16)) {    return substr($result, 26);  } else {   return '';  } } else { $ustr = $keyc.str_replace('=', '', base64_encode($result)); $ustr = str_replace('+','[a]',$ustr); $ustr = str_replace('&','[b]',$ustr); $ustr = str_replace('/','[c]',$ustr);  return $ustr; }}