function doesn't return anything in php
Question
I have a problem with this function, it doesn't return anything for me, I don't know the cause I want to obtaining the xor of the both of string `
<?php
if ($_SERVER['REQUEST_METHOD'] == "POST") {
if (array_key_exists("back", $_POST)) {
header('Location: index.php');
exit;
}
}
function xor_this($string) {
// Let's define our key here
$key = ('ma');
// Our plaintext/ciphertext
$text =$string;
// Our output text
$outText = '';
// Iterate through each character
for($i=0;$i<strlen($text);)
{
for($j=0;$j<strlen($key);$j++,$i++)
{
$outText .= $text{$i} ^ $key{$j};
echo 'i='.$i.', '.'j='.$j.', '.$outText{$i}.'<br />'; //for debugging
echo $outText;
}
}
return $outText;
}
?>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title></title>
</head>
<body>
<form name="confirm" action="index.php" method="POST">
<table>
<tr>
<td>La chaine a chiffrer :</td>
<td><?php echo $_POST['chaine']; ?></td>
</tr>
<tr>
<td>La cle de meme taille :</td>
<td><?php echo $_POST['cle']; ?></td>
</tr>
<tr>
<td>Le XOR :</td>
<td><?php echo xor_this($_POST['chaine']); ?></td>
</tr>
</table>
<input type="submit" name="back" value="retour"/>
</form>
</body>
</html>
`
do you any idea about this problem, I thank you in advance
--------------------edit--------------------------
I took into account your answers but the same problem : nothing is displayed on the string returned by the function here is the newly code :
<?php
session_start();
$flag = false;
function xor_this($chaine, $cle) {
$chiffre = '';
// Iterate through each character
for($i=0;$i<strlen($chiffre);)
{
$chiffre .= $chaine{$i} ^ $cle{$i};
echo $chiffre;
}
return $chiffre;
}
?>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title></title>
</head>
<body>
<?php
if ($_SERVER["REQUEST_METHOD"] == "POST") {
$data = array("chaine" => $_POST["chaine"], "cle" => $_POST["cle"]);
}
?>
<form name="logon" action="index.php" method="POST" >
<table>
<tr>
<td>La chaine a chiffrer :</td>
<td><input type="text" name="chaine" value="<?php if (!empty($data["chaine"])) echo $data["chaine"]; else echo ""; ?>" ></td>
</tr>
<tr>
<td>La cle de meme taille :</td>
<td><input type="text" name="cle" value="<?php if (!empty($data["cle"])) echo $data["cle"]; else echo ""; ?>" ></td>
<td>
<?php
if ($_SERVER["REQUEST_METHOD"] == "POST") {
if (strlen($_POST['chaine']) <> strlen($_POST['cle']))
echo "la chaine et la cle sont de taille differente";
}
?>
</td>
</tr>
</table>
<input type="submit" value="Chiffrer">
<table>
<tr>
<td>La chaine chiffre : </td>
<td>
<?php
if ($_SERVER["REQUEST_METHOD"] == "POST") {
if (strlen($_POST['chaine']) == strlen($_POST['cle']))
echo bin2hex(xor_this($_POST["chaine"],$_POST["cle"]));
}
?>
</td>
</tr>
</table>
</form>
</body>
</html>
do you have any other idea, thanks
1 answers
solution1
1 2012-11-12 12:25:38
Your code is almost correct. The primary issue is, that all lower-case letters will fall outside the printable range.
You can use bin2hex() to see what the result is in hexadecimal:
bin2hex(xor_this($string));
Considering only lower case letters, the ASCII range is: [97, 122] or in binary:
0110_0001
0111_1010
What this means is, that for one lowecase letter, the result is always going to look like this: 000x_xxxx .
The highest number you could get is the following: 0001_1111 , that's 31 , so all lower case letters will map to nonprintable characters.
A better for loop
You could fix the edge-case as pointed out by Jon when the $text is shorter than $key by introducing an additional condition in the inner loop.
However, consider the following alternative:
$key = str_pad("", strlen($text), "ma");
for($i = 0; $i < strlen($text); $i++) {
$outText .= $text[i] ^ $key[$i];
}
The technical post webpages of this site follow the CC BY-SA 4.0 protocol. If you need to reprint, please indicate the site URL or the original address.Any question please contact:yoyou2525@163.com.