Detailed explanation of PHP encryption and decryption class examples

<?php
function i_array_column($input, $columnKey, $indexKey=null){
if(!function_exists(&#39;array_column&#39;)){
$columnKeyIsNumber = (is_numeric($columnKey))?true:false;
$indexKeyIsNull = (is_null($indexKey))?true :false;
$indexKeyIsNumber = (is_numeric($indexKey))?true:false;
$result = array();
foreach((array)$input as $key=>$row){
if($columnKeyIsNumber){
$tmp= array_slice($row, $columnKey, 1);
$tmp= (is_array($tmp) && !empty($tmp))?current($tmp):null;
}else{
$tmp= isset($row[$columnKey])?$row[$columnKey]:null;
}
if(!$indexKeyIsNull){
if($indexKeyIsNumber){
$key = array_slice($row, $indexKey, 1);
$key = (is_array($key) && !empty($key))?current($key):null;
$key = is_null($key)?0:$key;
}else{
$key = isset($row[$indexKey])?$row[$indexKey]:0;
}
}
$result[$key] = $tmp;
}
return $result;
}else{
return array_column($input, $columnKey, $indexKey);
}
}
function randcode($len, $mode = 2){
$rcode = &#39;&#39;;
switch($mode){
case 1: //去除0、o、O、l等易混淆字符
$chars = &#39;ABCDEFGHJKLMNPQRSTUVWXYZ23456789abcdefghijkmnpqrstuvwxyz&#39;;
break;
case 2: //纯数字
$chars = &#39;0123456789&#39;;
break;
case 3: //全数字+大小写字母
$chars = &#39;ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789abcdefghijklmnopqrstuvwxyz&#39;;
break;
case 4: //全数字+大小写字母+一些特殊字符
$chars = &#39;ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789abcdefghijklmnopqrstuvwxyz~!@#$%^&*()&#39;;
break;
}
$count = strlen($chars) - 1;
mt_srand((double)microtime() * 1000000);
for($i = 0; $i < $len; $i++) {
$rcode .= $chars[mt_rand(0, $count)];
}
return $rcode;
}
/**
* $string 明文或密文
* $operation 加密ENCODE或解密DECODE
* $key 密钥
* $expiry 密钥有效期
*/
function authcode($string, $operation = &#39;DECODE&#39;, $key = &#39;&#39;, $expiry = 0) {
$ckey_length = 4;
$key = md5($key);
$keya = md5(substr($key, 0, 16));
$keyb = md5(substr($key, 16, 16));
$keyc = $ckey_length ? ($operation == &#39;DECODE&#39; ? substr($string, 0, $ckey_length): substr(md5(microtime()), -$ckey_length)) : &#39;&#39;;
$cryptkey = $keya.md5($keya.$keyc);
$key_length = strlen($cryptkey);
$string = $operation == &#39;DECODE&#39; ? base64_decode(substr($string, $ckey_length)) : sprintf(&#39;%010d&#39;, $expiry ? $expiry + time() : 0).substr(md5($string.$keyb), 0, 16).$string;
$string_length = strlen($string);
$result = &#39;&#39;;
$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($operation == &#39;DECODE&#39;) {
if((substr($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 &#39;&#39;;
}
} else {
return $keyc.str_replace(&#39;=&#39;, &#39;&#39;, base64_encode($result));
}
}