Kali ini saya akan mempostingkan kembali tutorial tentang pengamanan kode pada Php, mungkin hanya sedikit atau beberapa file yang yang mungkin bisa di copy paste kan untuk digunakan pada form Php.Security code adalah suatu bentuk perlindungan terhadap suatu form dari serangan SPAM. Sebagai contoh pernakah kita mengisi formulir pendaftaran untuk mendapatkan email account di yahoo??
yang pertama Formulir akan menampilkan security code yang di generate oleh script PHP, apabila page tersebut di refresh maka security code akan di generate lagi sehingga berubah codenya hal ini sangat berguna sekali untuk menangkal serangan spam.
yang keduaSetelah di submit, script php akan memvalidasi data anda dan mencocok kan security code yang telah anda masuk kan apabila security code tidak sama, maka proses akan di batalkan apabila security code sama, maka proses akan dilanjutkan.
Berikut file-file yang akan kita gunakan :
1. script form.html
2. script action.php
3. script captchasecurityimages.php
4. file font

........script.......
1. script form.htm
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<form action="action.php" method="post">
Pesan: <input type="text" name="message" /><br />
<img src="captchasecurityimages.php?width=100&height=40&character=5" /><br />
Security Code: <input id="security_code" name="security_code" type="text" /><br />
<input type="submit" name="submit" value="Submit" />
</form>
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2. script action.php
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<?php
session_start();
if( isset($_POST['submit'])) {
if(($_SESSION['security_code'] == $_POST['security_code']) &&
(!empty($_SESSION['security_code'])) ) {
// masukkan script anda jika validasi benar
echo 'Terimakasih Pasan anda: "'.$_POST['message'].'"';
} else {
// masukkan script anda jika validasi salah
echo 'Sorry, anda memasukkan security code yang salah<br />';
include "form.htm";
}
} else {
include "form.htm";
}
?>
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3. script captchasecurityimages.php
============================================================
<?php
session_start();
class CaptchaSecurityImages {
var $font = 'monofont.ttf';
function generateCode($characters) {
/* list all possible characters, similar looking characters and vowels have been removed */
$possible = '23456789bcdfghjkmnpqrstvwxyz';
$code = '';
$i = 0;
while ($i < $characters) {
$code .= substr($possible, mt_rand(0, strlen($possible)-1), 1);
$i++;
}
return $code;
}
function CaptchaSecurityImages($width='120',$height='40',$characters='6') {
$code = $this->generateCode($characters);
/* font size will be 75% of the image height */
$font_size = $height * 0.75;
$image = @imagecreate($width, $height) or die('Cannot Initialize new GD image
stream');
/* set the colours */
$background_color = imagecolorallocate($image, 255, 255, 255);
$text_color = imagecolorallocate($image, 20, 40, 100);
$noise_color = imagecolorallocate($image, 100, 120, 180);
/* generate random dots in background */
for( $i=0; $i<($width*$height)/3; $i++ ) {
imagefilledellipse($image, mt_rand(0,$width), mt_rand(0,$height), 1, 1, $noise_color);
}
/* generate random lines in background */
for( $i=0; $i<($width*$height)/150; $i++ ) {
imageline($image, mt_rand(0,$width), mt_rand(0,$height), mt_rand(0,$width),
mt_rand(0,$height), $noise_color);
}
/* create textbox and add text */
$textbox = imagettfbbox($font_size, 0, $this->font, $code);
$x = ($width - $textbox[4])/2;
$y = ($height - $textbox[5])/2;
imagettftext($image, $font_size, 0, $x, $y, $text_color, $this->font , $code);
/* output captcha image to browser */
imagejpeg($image);
imagedestroy($image);
$_SESSION['security_code'] = $code;
}
}
$width = isset($_GET['width']) ? $_GET['width'] : '120';
$height = isset($_GET['height']) ? $_GET['height'] : '40';
$characters = isset($_GET['characters']) ? $_GET['characters'] : '6';
header('Content-Type: image/jpeg');
$captcha = new captchasecurityimages($width,$height,$characters);
?>
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4. file font
Gunakan font: monofont.ttf
#bisa di edit kembali dengan sesuai yang diinginkan !!!