PHP加解密

<?php
    $s='asdf';
    echo base64_encode($s); #base64加密
    echo base64_decode($s); #bsae64解密
    echo md5($s); #md5加密
    echo sha1($s); #sha1加密
    echo escape($s) #url加密
    echo escape($s) #url解密
?>

<?php #url完全加密
    $a=$_GET['a'];
    function fullescape($in){
        $out = '';
        for ($i=0;$i<strlen($in);$i++){
            $hex = dechex(ord($in[$i]));
            if ($hex=='')
            $out = $out.urlencode($in[$i]);
            else
            $out = $out .'%'.((strlen($hex)==1) ? ('0'.strtoupper($hex)):(strtoupper($hex)));
        }
        $out = str_replace('+','%20',$out);
        $out = str_replace('_','%5F',$out);
        $out = str_replace('.','%2E',$out);
        $out = str_replace('-','%2D',$out);
        return $out;
    }
    echo fullescape($a);
?>