PHP simple verification code: random distortion of letters + numbers

Now there are various types of verification codes. I personally think that the verification code is for users to see, so it is easy. What interference codes, skews, and complex backgrounds are all a kind of torture to users. The website verification codes with relatively large experience are relatively simple and there is no complicated background and no interference code... syntaxHighlighter. all (); now all kinds of verification codes, I personally think that the verification code is for users to see, so it is easy. What interference codes, skews, and complex backgrounds are all a kind of torture to users.
Website verification codes with relatively large experience are relatively simple, with no complex background, no interference code, and no background.
If something is not well written, you are welcome to criticize and give some advice.
[Php]
If (! Defined ('is _ initphp') exit ('Access Denied! ');
/*************************************** **************************************** **
* InitPHP 2.0 domestic PHP development framework extension class library-verification code
*-------------------------------------------------------------------------------
* CopyRight: CopyRight By initphp.com
* You can use the source code freely, but keep the author information during use. Respecting Others means respecting yourself.
*-------------------------------------------------------------------------------
* $ Author: liuxinming
* $ Dtime: 2012-10-09
**************************************** **************************************** ***/
Class seccodeInit {
Private $ width;
Private $ height;
Private $ type = 0; // 0 letters + digit verification code
Private $ time = 3000; // verification code Expiration time (s)
Private $ color = null; // font color of the verification code
Private $ im;
Private $ length = 4; // verification code length
Private $ warping; // random twist

/**
* Obtain random values
* @ Return string
*/
Private function get_random_val (){
$ I = 0;
While ($ I <$ this-> length)
{
Mt_srand (double) microtime () * 1000000 );
$ Randnum = mt_rand (50, 90 );
If (! In_array ($ randnum, array (58,59, 60,61, 62,63, 64,73, 79 )))
{
$ Authnum = $ authnum. chr ($ randnum );
$ I ++;
}
}
Session_start ();
$ Time = time ();
$ Checkcode = md5 (md5 ($ authnum. 'initphpyzmsy'. $ time ));
$ Key = $ time. ','. $ checkcode. ','. authnum;
$ _ SESSION ['initphp _ Code'] = $ key;
Return $ authnum;
}

/**
* Obtain the verification code Image
* @ Param $ width
* @ Param $ height
* @ Param $ warping random font distortion switch 0 = off, 1 = on
* @ Return string
*/
Public function getcode ($ width = 140, $ height = 40, $ warping = 0 ){
$ This-> width = $ width;
$ This-> height = $ height;
$ This-> warping = $ warping;
If ($ this-> type <2 & function_exists ('imagecreate') & function_exists ('imagecolorset') & function_exists ('imagecopyresized ') & function_exists ('imagecolorallocate') & function_exists ('imagechar ') & function_exists ('imagecolorsforindex ')&&
Function_exists ('imageline ') & function_exists ('imagecreatefromstring') & (function_exists ('imagegif') | function_exists ('imagepng ') | function_exists ('imagejpeg '))){
$ This-> image ();
}
}
/**
* Generate an image verification code
* @ Return string
*/
Public function image (){
$ This-> im = imagecreate ($ this-> width, $ this-> height); // you can specify the image background size.
Imagecolorallocate ($ this-> im, 243,251,254); // set the background
$ This-> color = imagecolorallocate ($ this-> im, mt_rand (1,120), mt_rand (1,120), mt_rand (1,120); // random color of the font of the verification code
$ TtfPath = dirname (_ FILE _). '/font/'; // font directory
$ Dirs = opendir ($ ttfPath );
$ Seccodettf = array ();
While ($ entry = readdir ($ dirs )){
If ($ entry! = '.' & $ Entry! = '.. '& In_array (strtolower (addslashes (strtolower (substr (strrchr ($ entry ,'. '), 1, 10), array ('ttf', 'ttc '))){

$ Seccodettf [] = $ ttfPath. $ entry;
}
}
$ Ttf = $ seccodettf [array_rand ($ seccodettf)]; // random font
$ Size = $ this-> type? $ This-> width/7: $ this-> width/6; // font size
Imagettftext ($ this-> im, $ size, 0, 10, $ size * 1.2, $ this-> color, $ ttf, $ this-> get_random_val ()); // Set verification code characters
If ($ this-> warping) {// random twist
$ This-> setWarping ();
}
If (function_exists ("imagepng "))
{
Header ("Content-type: image/png ");
$ Code = imagepng ($ this-> im );
} Elseif (function_exists ("imagejpeg "))
{
Header ("Content-type: image/jpeg ");
$ Code = imagejpeg ($ this-> im );
} Elseif (function_exists ("imagegif "))
{
Header ("Content-type: image/gif ");
$ Code = imagegif ($ this-> im );
}
Imagedestroy ($ this-> im );
Return $ code;
}

/**
* Check the verification code
* @ Param $ code
* @ Return bool
*/
Public function checkCode ($ code ){
Session_start ();
$ Secode = explode (',', $ _ SESSION ['initphp _ Code']);
$ Time = time ();
// Check whether the time has expired
If ($ secode [0]> $ time | $ time-$ secode [0]> $ this-> time)
{
Return false;
}
// Whether the verification code is consistent after the two-md5 key pairs
If ($ secode [1] <> md5 (md5 ($ code. 'initphzmsy'. $ secode [0]) {
Return false;
}
// Check whether the verification code string is consistent
If ($ code | $ code <> $ secode [2])
{
Return false;
}
Return true;
}

/* Random twist */
Public function setWarping (){
$ Rgb = array ();
$ Direct = rand (0, 1 );
$ Width = imagesx ($ this-> im );
$ Height = imagesy ($ this-> im );
$ Level = $ width/20;
For ($ j = 0; $ j <$ height; $ j ++ ){
For ($ I = 0; $ I <$ width; $ I ++ ){
$ Rgb [$ I] = imagecolorat ($ this-> im, $ I, $ j );
}
For ($ I = 0; $ I <$ width; $ I ++ ){
$ R = sin ($ j/$ height * 2 * M_PI-M_PI * 0.5) * ($ direct? $ Level:-$ level );
Imagesetpixel ($ this-> im, $ I + $ r, $ j, $ rgb [$ I]);
}
}
}
}
?>
Effect: