PHP 加密与解密

<meta charset="UTF-8">
<?php
function encrypt($data, $key){
	$key = md5($key);
	$x  = 0;
	$len = strlen($data);
	$l  = strlen($key);
	for ($i = 0; $i < $len; $i++){
		if ($x == $l){
			$x = 0;
		}
		$char .= $key{$x};
		$x++;
	}
	for ($i = 0; $i < $len; $i++){
		$str .= chr(ord($data{$i}) + (ord($char{$i})) % 256);
	}
	return base64_encode($str);
}
function decrypt($data, $key){
	$key = md5($key);
	$x = 0;
	$data = base64_decode($data);
	$len = strlen($data);
	$l = strlen($key);
	for ($i = 0; $i < $len; $i++){
		if ($x == $l) {
			$x = 0;
		}
		$char .= substr($key, $x, 1);
		$x++;
	}
	for ($i = 0; $i < $len; $i++){
		if (ord(substr($data, $i, 1)) < ord(substr($char, $i, 1))){
			$str .= chr((ord(substr($data, $i, 1)) + 256) - ord(substr($char, $i, 1)));
		}else{
			$str .= chr(ord(substr($data, $i, 1)) - ord(substr($char, $i, 1)));
		}
	}
	return $str;
}
$data = 'http://onestopweb.iteye.com/';  // 被加密信息
$key = 'www.phpsong.com';     // 密钥
$encrypt = encrypt($data, $key);
$decrypt = decrypt($encrypt, $key);
echo '字符串：'.$data. '<br/>加密后：'.$encrypt. '<br/>解密后：'. $decrypt;

效果图：