<?php

/*

 * @param $string 要加密或解决的字符串

 * @param $operation 加密/解密 ENCODE加密, DECODE 解密

 * @param $key 加密/解决因子

*/

function authcode($string, $operation = 'DECODE', $key = '12345678', $expiry = 0) {

    	$ckey_length = 4;

    	$key  = md5($key);

    	$keya = md5(substr($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 {

    		return $keyc.str_replace('=', '', base64_encode($result));

    	}

    }

// 加密 $ok

$str = '123456';

$ok = authcode($str, 'ENCODE');

echo $ok , "<br />";

// 解密 $ok1

$ok1 = authcode($ok, 'DECODE');

echo $ok1;

?>