Codice PHP:
<?php
$pdo = new PDO('mysql:host=localhost;dbname=captcha', 'root', '');
$stmt = $pdo->prepare("SELECT * FROM validation WHERE url_key = ? AND expire_date > NOW()");
$stmt->execute(array($_GET['token']));
$row = $stmt->fetch(PDO::FETCH_ASSOC);
$texture = imagecreatefrompng('texture.png');
$source = imagecolorat($texture, rand(0, imagesx($texture)), rand(0, imagesy($texture)));
$r = ($source >> 16 & 0xff) + 50;
$g = ($source >> 8 & 0xff) + 50;
$b = ($source & 0xff) + 50;
$text_color = imagecolorallocate($texture, $r, $g, $b);
imagestring($texture, 5, (imagesx($texture) - strlen($row['captcha']) * 5)/ 2, 5, $row['captcha'], $text_color);
header('Content-Type: image/png');
imagepng($texture);
imagedestroy($texture);
unction random_string($len)
{
$string = "";
$chars = array("a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k",
"l", "m", "n", "o", "p", "q", "r", "s", "t", "u", "v",
"w", "x", "y", "z", "A", "B", "C", "D", "E", "F", "G",
"H", "I", "J", "K", "L", "M", "N", "O", "P", "Q", "R",
"S", "T", "U", "V", "W", "X", "Y", "Z", "0", "1", "2",
"3", "4", "5", "6", "7", "8", "9");
for($i = 0; $i < $len; ++$i)
{
shuffle($chars);
$string .= $chars[0];
}
return $string;
}
$message = 'Inserisci la scringa alphanumerica per effettuare la validazione:';
$pdo = new PDO('mysql:host=localhost;dbname=captcha', 'root', '');
$pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
if(isset($_POST['validate_token']))
{
// Eseguo la validazione
$stmt = $pdo->prepare("SELECT * FROM validation WHERE url_key = ? AND expire_date > NOW()");
$stmt->execute(array($_POST['token']));
$row = $stmt->fetch(PDO::FETCH_ASSOC);
$message = ($row && ($row['captcha'] == $_POST['validate_token'])) ? 'token corretto' : 'token [b]NON[/b] corretto';
$stmt = $pdo->prepare("DELETE FROM validation WHERE url_key = ?");
$stmt->execute(array($_POST['token']));
}
// Elimino tutti i record scaduti
$pdo->query("DELETE FROM validation WHERE expire_date <= NOW()");
// Genero casualmente un record per la tabella validation
$url_key = sha1(uniqid(rand(), true)); // Possiamo (e dovremmo) fare meglio
$captcha = random_string(6);
$stmt = $pdo->prepare("INSERT INTO validation (id, url_key, captcha, expire_date) VALUES ('', ?, ?, DATE_ADD(NOW(), INTERVAL 5 MINUTE))");
$stmt->execute(array($url_key, $captcha));
?>
<html>
<head>
<title>CAPTCHA test</title>
</head>
<body>
<form method="POST" action="<?php echo $_SERVER['PHP_SELF']; ?>">
<input type="hidden" name="token" value="<?php echo $url_key; ?>" />
<?php echo $message; ?>
</p>
[img]captcha.php?token=<?php echo $url_key; ?>[/img]
<input type="text" name="validate_token" />
<input type="submit" name="action" value="Test" />
</form>
</body>
</html>
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