str_replace
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;
}
?>
str_rot13
(PHP 4 >= 4.2.0, PHP 5)
str_rot13 — 文字列に rot13 変換を行う
説明
string str_rot13
( string $str
)
Performs the ROT13 encoding on the str argument and returns the resulting string.
ROT13 は、各文字をアルファベット順に 13 文字シフトさせ、 アルファベット以外の文字はそのままとするエンコードを行います。 エンコードとデコードは同じ関数で行われます。 引数にエンコードされた文字列を指定した場合には、元の文字列が返されます。
パラメータ
- str
-
入力文字列。
返り値
指定した文字列を ROT13 変換した結果を返します。
例
例1 str_rot13() の例
<?php
echo str_rot13('PHP 4.3.0'); // CUC 4.3.0
?>
変更履歴
| バージョン | 説明 |
|---|---|
| 4.3.0 | この関数の挙動が修正されました。以前のバージョンでは、 str 自体も変更されてしまっていました。 ちょうど、参照渡しで渡したときと同じような挙動だったのです。 |
add a note
User Contributed Notesstr_rot13
shaunspiller at spammenotgmail dot com
26-Sep-2009 03:54
26-Sep-2009 03:54
peter at NOSPAM jamit dot com
07-Sep-2009 02:31
07-Sep-2009 02:31
This ROT13 variant is different from my earlier version in that it retains 'ethnicity'. For example, a Chinese text when encrypted will remain Chinese, and the string will not be making sense (the real meaning will be encrypted). Just look at the code and you will understand.
<?php
function unichar2ords($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 "Ñ 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 08:11
07-Sep-2009 08:11
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
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 04:01
08-Aug-2007 04:01
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 08:11
11-Jul-2007 08:11
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 07:21
31-May-2007 07:21
<?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
25-May-2007 11:30
25-May-2007 11:30
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.