字符串函数
在线手册：中文 英文
PHP手册

str_rot13

(PHP 4 >= 4.2.0, PHP 5)

str_rot13 — 对字符串执行 ROT13 转换

说明

string str_rot13 ( string $str )

对 str 参数执行 ROT13 编码并将结果字符串返回。

ROT13 编码简单地使用字母表中后面第 13 个字母替换当前字母，同时忽略非字母表中的字符。编码和解码都使用相同的函数，传递一个编码过的字符串作为参数，将得到原始字符串。

参数

str

输入字符串。

返回值

返回给定字符串的 ROT13 版本。

范例

Example #1 str_rot13() 范例

<?php

echo str_rot13('PHP 4.3.0'); // CUC 4.3.0

?>

更新日志

版本 说明
4.3.0 函数行为被修正。在此修正之前，str 参数也会被改变，因为它是通过引用传递的。

字符串函数
在线手册：中文 英文
PHP手册
PHP手册 - N: 对字符串执行 ROT13 转换

用户评论:

shaun (11-Feb-2012 10:44)

I was reminded again of the desire for a generic str_rot function. Character manipulation loops in PHP are slow compared to their C counterparts, so here's a tuned version of the previous function I posted. It's 1.6 times as fast, mainly by avoiding chr() calls.

<?php
function str_rot($s, $n = 13) {
    static $letters = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';
    $n = (int)$n % 26;
    if (!$n) return $s;
    if ($n == 13) return str_rot13($s);
    for ($i = 0, $l = strlen($s); $i < $l; $i++) {
        $c = $s[$i];
        if ($c >= 'a' && $c <= 'z') {
            $s[$i] = $letters[(ord($c) - 71 + $n) % 26];
        } else if ($c >= 'A' && $c <= 'Z') {
            $s[$i] = $letters[(ord($c) - 39 + $n) % 26 + 26];
        }
    }
    return $s;
}
?>

But using strtr() you can get something 10 times as fast as the above :

<?php
function str_rot($s, $n = 13) {
    static $letters = 'AaBbCcDdEeFfGgHhIiJjKkLlMmNnOoPpQqRrSsTtUuVvWwXxYyZz';
    $n = (int)$n % 26;
    if (!$n) return $s;
    if ($n < 0) $n += 26;
    if ($n == 13) return str_rot13($s);
    $rep = substr($letters, $n * 2) . substr($letters, 0, $n * 2);
    return strtr($s, $letters, $rep);
}
?>

This technique is faster because PHP's strtr is implemented in C using a byte lookup table (it has O(m + n) complexity). However, PHP 6 will use Unicode, so I guess(?) strtr will then have to be implemented with a search for each character (O(m * n)). Using strtr might still be faster since it offloads the character manipulation to C rather than PHP, but I don't really know. Take your pick.

Happy coding!

(Benchmark code):

<?php
for ($k = 0; $k < 10; $k++) {
    $s = 'The quick brown fox jumps over the lazy dog.';
    $t = microtime(1);
    for ($i = 0; $i < 1000; $i++) $s = str_rot($s, $i);
    $t = microtime(1) - $t;
    echo number_format($t, 3) . "\n";
}
?>

shaunspiller at spammenotgmail dot com (26-Sep-2009 04:54)

Here's my implementation of a str_rot that takes a custom offset. It's faster than the others here because it allocates the output string in one go instead of tacking on characters one at a time. It can handle positive or negative offsets of any size, and it fixes everything up to ensure only upper and lower case letters are translated and that they wrap around correctly within the alphabet.

<?php
function str_rot($s, $n = 13) {
    $n = (int)$n % 26;
    if (!$n) return $s;
    for ($i = 0, $l = strlen($s); $i < $l; $i++) {
        $c = ord($s[$i]);
        if ($c >= 97 && $c <= 122) {
            $s[$i] = chr(($c - 71 + $n) % 26 + 97);
        } else if ($c >= 65 && $c <= 90) {
            $s[$i] = chr(($c - 39 + $n) % 26 + 65);
        }
    }
    return $s;
}
?>

peter at NOSPAM jamit dot com (07-Sep-2009 03:31)

This ROT13 variant is different from my earlier version in that it retains 'ethnicity'. For example, a Chinese text when encrypted will remain Chinese, and the string will not be making sense (the real meaning will be encrypted). Just look at the code and you will understand.

<?php

function unichar2ords($char, $encoding = 'UTF-8') {       
    $char = mb_convert_encoding($char, 'UCS-4', $encoding);
    $val = unpack('N', $char);           
    return $val[1];
    }

function ords2unichar($ords, $encoding = 'UTF-8'){
    $char = pack('N', $ords);
    return mb_convert_encoding($char, $encoding, 'UCS-4');           
    }

function mbStringToArray ($string, $encoding = 'UTF-8') {
    if (empty($string)) return false;
    for ($strlen = mb_strlen($string, $encoding); $strlen > 0; ) {
        $array[] = mb_substr($string, 0, 1, $encoding);
        $string  = mb_substr($string, 1, $strlen, $encoding);
        $strlen  = $strlen - 1;
        }
    return $array;
    }

function unicodeRotN($str, $offset, $encoding = 'UTF-8') {
    $val = '';
    $array = mbStringToArray ($str, $encoding = 'UTF-8');
    $len = count($array);
    for ($i = 0; $i < $len; $i++) {
        $val .= ords2unichar(unichar2ords($array[$i], $encoding) + $offset, $encoding);
        }
    return $val;
    }

// example

$original = '中國是我的家'; // means "China is my home"

$encrypted = unicodeRotN($string, 13); // 为團昼戞皑寃 means "? Ai injustice for the Mission Day" (Google translation)

$decrypted = unicodeRotN($encrypted, -13); // 中國是我的家

?>

peter at NOSPAM jamit dot com (07-Sep-2009 09:11)

Here is my ROT13 function that works for all possible characters and not just ASCII. It can be used on Chinese, Japanese, ....

<?php

function rot13encrypt ($str) {
    return str_rot13(base64_encode($str));
    }

function rot13decrypt ($str) {
    return base64_decode(str_rot13($str));
    }

// example

$string = '中國是我的家';

$encrypted = rot13encrypt ($string); // produces 5Yvg5MlY5cvi5bvE55dR5n62

$decrypted = rot13decrypt ($encrypted); // produces 中國是我的家

?>

grawity+phpnet at gmail dot com (31-Dec-2007 01:39)

resubmitting updated function in re:#76975
<?php
function asc_shift($str,$offset=0) {
    $new = '';
    for ($i = 0; $i < strlen($str); $i++)
        $new .= chr(ord($str[$i])+$offset);
    return $new;
}
?>
because as of PHP 6, $str{$i} is deprecated.

nick at lazy-river dot net (08-Aug-2007 05:01)

This is recursive function to shift the component letters of a string left or right in the ascii table.

I've left it simple as it suits my needs, but you may want to include error checking for a null string and also put bounds in place, or make it actually rotate around the whole character set rather than just shifting the string up or down.

function asc_shift($string, $amount) {
  $key = substr($string, 0, 1);
  if(strlen($string)==1) {
    return chr(ord($key) + $amount);
  } else {
    return chr(ord($key) + $amount) . asc_shift(substr($string, 1, strlen($string)-1), $amount);
  }
}

For example:
<?php
echo asc_shift("TESTING12345@", 5);
?>

shifts every character up 5 ascii positions, resulting in this string:

YJXYNSL6789:E

In reverse:

<?php
echo asc_shift("YJXYNSL6789:E", -5);
?>

shifts every character down 5 ascii positions, resulting in this string:

TESTING12345@

arwab at surrealwebs dot com (11-Jul-2007 09:11)

here's my rot function, it works anyway
<?php
/**
 * preforms the rotation algorithm on the passed in string
 */
function _rot( $str , $dist=13 ){
    if( !is_numeric($dist) || $dist < 0){
        $dist = 13;
    }

    $u_lower =  65; $u_upper =  90;
    $l_lower =  97; $l_upper = 122;
   
    $char_count = ($u_upper - $u_lower) +1;

    while( $dist > $char_count ){
        $dist -= $char_count;
    }

    $newstr = '';
   
    for( $i=0; $i<strlen($str); ++$i){
        $c = ord($str[$i]);

        /*
         * Check if the character is within the bounds of our function (a-zA-z)
         * if not it gets tacked on to the string as is and we move on to the
         * next one.
         */
        if( $c<$u_lower || $c>$l_upper || ( $c>$u_upper && $c <$l_lower ) ){
            $newstr .= chr($c);
            continue;
        }

        $lower = ( $c<=$u_upper?$u_lower:$l_lower);
        $upper = ( $c<=$u_upper?$u_upper:$l_upper);

        $c += $dist;

        if( $c > $upper){
            $c = (($c - $upper) + ($lower-1));
        }

        $newstr .= chr($c);
    }
   
    return $newstr;
}
?>

electro at whatever dot com (31-May-2007 08:21)

<?php

/**
 * Rotate each string characters by n positions in ASCII table
 * To encode use positive n, to decode - negative.
 * With n = 13 (ROT13), encode and decode n can be positive.
 *
 * @param string $string
 * @param integer $n
 * @return string
 */
function rotate($string, $n) {
   
    $length = strlen($string);
    $result = '';
   
    for($i = 0; $i < $length; $i++) {
        $ascii = ord($string{$i});
       
        $rotated = $ascii;
       
        if ($ascii > 64 && $ascii < 91) {
            $rotated += $n;
            $rotated > 90 && $rotated += -90 + 64;
            $rotated < 65 && $rotated += -64 + 90;
        } elseif ($ascii > 96 && $ascii < 123) {
            $rotated += $n;
            $rotated > 122 && $rotated += -122 + 96;
            $rotated < 97 && $rotated += -96 + 122;
        }
       
        $result .= chr($rotated);
    }
   
    return $result;
}

$enc = rotate('string', 6);
echo "Encoded: $enc<br/>\n";
echo 'Decoded: ' . rotate($enc, -6);

?>

maximius at gmail dot com (26-May-2007 12:30)

Perhaps someone will find this useful ;)

<?
           function rotN($s, $n){
                $s2 = "";
                for($i = 0; $i < strlen($s); $i++){
                    $char2 = $char = ord($s{$i});
                    $cap = $char & 32;

                    $char &= ~ $cap;
                    $char = $char > 64 && $char < 123 ? (($char - 65 + $n) % 26 + 65) : $char;
                    $char |= $cap;
                    if($char < 65 && $char2 > 64 || ($char > 90 && $char < 97 && ($char2 < 91 || $char2 > 96))) $char += 26;
                    else if($char > 122 && $char2 < 123) $char -= 52;
                    if(strtoupper(chr($char2)) === chr($char2)) $char = strtoupper(chr($char)); else $char = strtolower(chr($char));
                    $s2 .= $char;
                }
                return $s2;
            }
?>
It takes any string, $s, and any ROT value, $n. Just like str_rot13, it's both an encoder and decoder. To decode an encoded string, just pass -$n instead of $n.