CI驗證碼的使用

最簡單的調用：

public function show(){
  $vals = array(
    'word' => 'Random word',
    'img_path' => './captcha/',  //位於根目錄下captcha
    'img_url' => 'http://www.ci.com/captcha/',  //一定要加http://
    'font_path' => './path/to/fonts/texb.ttf',
    'img_width' => '150',
    'img_height' => 30,
    'expiration' => 7200
    );
   $cap = create_captcha($vals);
   echo $cap['image'];
   }

注意：一定要記得$this->load->helper('captcha');

通過session驗證驗證碼

通過ajax動態改變驗證碼，實現“看不清，換一個功能”；

<div class="yzm">
        <img src="" width="77" height="27" />
 </div>

通過ajax改變<img>標籤的SRC；

把得到的值放入session；

function get_authcode() {
$CI = & get_instance ();
$CI->load->helper ( "captcha" );
$auth_array = ow_auth ();
$CI->session->set_userdata('auth_code', $auth_array ['word']);
return $auth_array;
}

function ow_auth() {
$vals = array (
'word' => _getRandCode (), 
'img_path' => './uploadfile/captcha/', 
'img_url' => '/uploadfile/captcha/', 
'img_width' => 70, 
'img_height' => 29, 
'expiration' => 200 
);
$cap = create_captcha ( $vals );
if (! $cap)
echo "something woring!";
return $cap;
}

自己指定驗證碼顯示類型以及顯示個數：

function _getRandCode($length = 4) {
$code_list = "ABCDEFGHJKLMNPQRSTUVWXYZ23456789";
$code_length = strlen ( $code_list ) - 1;

$rand_code = "";

for($i = 0; $i < $length; $i ++) {
$rand_num = rand ( 0, $code_length );
$rand_code .= $code_list [$rand_num];
}

return $rand_code;
}

系統函數重寫

function create_captcha($data = '', $img_path = '', $img_url = '', $font_path = '')
{
$defaults = array('word' => '', 'img_path' => '', 'img_url' => '', 'img_width' => '100', 'img_height' => '30', 'font_path' => '', 'expiration' => 7200);


foreach ($defaults as $key => $val)
{
if ( ! is_array($data))
{
if ( ! isset($$key) OR $$key == '')
{
$$key = $val;
}
}
else
{
$$key = ( ! isset($data[$key])) ? $val : $data[$key];
}
}


if ($img_path == '' OR $img_url == '')
{
return FALSE;
}


if ( ! @is_dir($img_path))
{
return FALSE;
}


if ( ! is_writable($img_path))
{
return FALSE;
}


if ( ! extension_loaded('gd'))
{
return FALSE;
}


// -----------------------------------
// Remove old images
// -----------------------------------


list($usec, $sec) = explode(" ", microtime());
$now = ((float)$usec + (float)$sec);


$current_dir = @opendir($img_path);


while ($filename = @readdir($current_dir))
{
if ($filename != "." and $filename != ".." and $filename != "index.html")
{
$name = str_replace(".jpg", "", $filename);


if (($name + $expiration) < $now)
{
@unlink($img_path.$filename);
}
}
}


@closedir($current_dir);


// -----------------------------------
// Do we have a "word" yet?
// -----------------------------------


  if ($word == '')
  {
$pool = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';


$str = '';
for ($i = 0; $i < 8; $i++)
{
$str .= substr($pool, mt_rand(0, strlen($pool) -1), 1);
}


$word = $str;
  }


// -----------------------------------
// Determine angle and position
// -----------------------------------


$length = strlen($word);
$angle = ($length >= 6) ? rand(-($length-6), ($length-6)) : 0;
$x_axis = rand(6, (360/$length)-16);
$y_axis = ($angle >= 0 ) ? rand($img_height, $img_width) : rand(6, $img_height);


// -----------------------------------
// Create image
// -----------------------------------


// PHP.net recommends imagecreatetruecolor(), but it isn't always available
if (function_exists('imagecreatetruecolor'))
{
$im = imagecreatetruecolor($img_width, $img_height);
}
else
{
$im = imagecreate($img_width, $img_height);
}


// -----------------------------------
//  Assign colors
// -----------------------------------


$bg_color = imagecolorallocate ($im, 255, 255, 255);
$border_color = imagecolorallocate ($im, 153, 102, 102);
$text_color = imagecolorallocate ($im, 214, 103, 103);
$grid_color = imagecolorallocate($im, 255, 182, 182);
$shadow_color = imagecolorallocate($im, 255, 240, 240);


// -----------------------------------
//  Create the rectangle
// -----------------------------------


ImageFilledRectangle($im, 0, 0, $img_width, $img_height, $bg_color);


// -----------------------------------
//  Create the spiral pattern
// -----------------------------------


$theta = 1;
$thetac = 17;
$radius = 16;
$circles = 20;
$points = 32;


for ($i = 0; $i < ($circles * $points) - 1; $i++)
{
$theta = $theta + $thetac;
$rad = $radius * ($i / $points );
$x = ($rad * cos($theta)) + $x_axis;
$y = ($rad * sin($theta)) + $y_axis;
$theta = $theta + $thetac;
$rad1 = $radius * (($i + 1) / $points);
$x1 = ($rad1 * cos($theta)) + $x_axis;
$y1 = ($rad1 * sin($theta )) + $y_axis;
imageline($im, $x, $y, $x1, $y1, $grid_color);
$theta = $theta - $thetac;
}


// -----------------------------------
//  Write the text
// -----------------------------------


$use_font = ($font_path != '' AND file_exists($font_path) AND function_exists('imagettftext')) ? TRUE : FALSE;


if ($use_font == FALSE)
{
$font_size = 5;
$x = rand(0, $img_width/($length/1.5));
$y = 0;
}
else
{
$font_size = 16;
$x = rand(0, $img_width/($length/1.5));
$y = $font_size+2;
}


for ($i = 0; $i < strlen($word); $i++)
{
if ($use_font == FALSE)
{
$y = rand(0 , $img_height/2);
imagestring($im, $font_size, $x, $y, substr($word, $i, 1), $text_color);
$x += ($font_size*2);
}
else
{
$y = rand($img_height/2, $img_height-3);
imagettftext($im, $font_size, $angle, $x, $y, $text_color, $font_path, substr($word, $i, 1));
$x += $font_size;
}
}




// -----------------------------------
//  Create the border
// -----------------------------------


imagerectangle($im, 0, 0, $img_width-1, $img_height-1, $border_color);


// -----------------------------------
//  Generate the image
// -----------------------------------


$img_name = $now.'.jpg';


ImageJPEG($im, $img_path.$img_name);


$img = "<img src=\"$img_url$img_name\" width=\"$img_width\" height=\"$img_height\" style=\"border:0;\" alt=\" \" />";


ImageDestroy($im);


return array('word' => $word, 'time' => $now, 'image' => $img);
}

知識補充：

php隨機數：

rand() 函數返回隨機整數。
rand(min,max)
如果沒有提供可選參數 min 和 max，rand() 返回 0 到 RAND_MAX 之間的僞隨機整數。例如，想要 5 到 15（包括 5 和 15）之間的隨機數，用 rand(5, 15)

mt_rand(min,max)
如果沒有提供可選參數 min 和 max，mt_rand() 返回 0 到 RAND_MAX 之間的僞隨機數。例如想要 5 到 15（包括 5 和 15）之間的隨機數，用 mt_rand(5, 15)。
該函數用了 Mersenne Twister 中已知的特性作爲隨機數發生器，它可以產生隨機數值的平均速度比 libc 提供的 rand() 快四倍。

php隨機字符串：

function generate_password( $length = 8 ) {
    $chars = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';
    $password = '';
    for ( $i = 0; $i < $length; $i++ ) 
    {
       //兩種方法
        // $password .= substr($chars, mt_rand(0, strlen($chars) - 1), 1);
          $password .= $chars[ mt_rand(0, strlen($chars) - 1) ];
    }
    return $password;
}

參數說明：

"expiration" (秒) 指定了驗證碼圖片的超時刪除時間. 默認是2小時

在system/helpers/captcha_helper.php中的create_captcha()函數，實現了驗證碼生成的功能，通過重寫該函數或者是重寫該類對驗證碼的其他一些參數進行設置！！！！