具有时效性的php加密解密函数代码

<?php
function encode_pass($tex,$key,$type="encode",$expiry=0){
    $chrarr=array('a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z',
                  'a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z',
                  '0','1','2','3','4','5','6','7','8','9');
    if($type=="decode"){
        if(strlen($tex)<14)return false;
        $verity_str=substr($tex, 0,8);
        $tex=substr($tex, 8);
        if($verity_str!=substr(md5($tex),0,8)){
            //完整性验证失败
            return false;
        }   
    }
    $key_b=$type=="decode"?substr($tex,0,6):$chrarr[rand()%62].$chrarr[rand()%62].$chrarr[rand()%62].$chrarr[rand()%62].$chrarr[rand()%62].$chrarr[rand()%62];

    $rand_key=$key_b.$key;   
    //设置时间选项
    $modnum=0;$modcount=0;$modcountstr="";
    if($expiry>0){
        if($type=="decode"){
            $modcountstr=substr($tex,6,1);
            $modcount=$modcountstr=="a"?10:floor($modcountstr);
            $modnum=substr($tex,7,$modcount);
            $rand_key=$rand_key.(floor((time()-$modnum)/$expiry));
        }else{
            $modnum=time()%$expiry;
            $modcount=strlen($modnum);
            $modcountstr=$modcount==10?"a":$modcount;

            $rand_key=$rand_key.(floor(time()/$expiry));           
        }
        $tex=$type=="decode"?base64_decode(substr($tex, (7+$modcount))):"xugui".$tex;
    }else{
        $tex=$type=="decode"?base64_decode(substr($tex, 6)):"xugui".$tex;
    }
    $rand_key=md5($rand_key);

    $texlen=strlen($tex);
    $reslutstr="";
    for($i=0;$i<$texlen;$i++){
        $reslutstr.=$tex{$i}^$rand_key{$i%32};
    }
    if($type!="decode"){
        $reslutstr=trim(base64_encode($reslutstr),"==");
        $reslutstr=$modcount?$modcountstr.$modnum.$reslutstr:$reslutstr;
        $reslutstr=$key_b.$reslutstr;
        $reslutstr=substr(md5($reslutstr), 0,8).$reslutstr;
    }else{
        if(substr($reslutstr,0, 5)!="xugui"){
            return false;
        }
        $reslutstr=substr($reslutstr, 5);
    }
    return $reslutstr;
}
$psa=encode_pass("woshi ceshi yong de ","taintainxousad","encode",120);
echo $psa;
echo "\r\n解密：";
echo encode_pass($psa,"taintainxousad",'decode',120);
?>