Analysis of php imitation QQ verification code examples

This article describes an example of a php-based QQ-like verification code, a verification code for QQ registration or logon. you have all seen it. the code provided in this article, you can also implement such a verification code. For more information, see.

The code is as follows:

/**
* QQ verification code imitation
*/
// Session save path
$ SessSavePath = dirname (_ FILE _). "/../data/sessions /";
If (is_writeable ($ sessSavePath) & is_readable ($ sessSavePath) {session_save_path ($ sessSavePath );}
Session_start ();
// Obtain random characters
$ Rndstring = '';
For ($ I = 0; $ I <4; $ I ++) $ rndstring. = chr (mt_rand (65,90 ));
$ Img_height = 45; // define the length and width of the image first.
$ Img_width = 10;
// If GD is supported, draw
If (function_exists ("imagecreate "))
{
// In some cases in Firefox, there will be multiple requests, and refreshing the page within 5 seconds will not change the session
$ Ntime = time ();
If (empty ($ _ SESSION ['DD _ ckstr_last ']) | empty ($ _ SESSION ['DD _ ckstr']) | ($ ntime-$ _ SESSION ['DD _ ckstr_last ']> 5 ))
{
$ _ SESSION ['DD _ ckstr'] = strtolower ($ rndstring );
$ _ SESSION ['DD _ ckstr_last '] = $ ntime;
}
$ Rndstring = $ _ SESSION ['DD _ ckstr'];
$ Rndcodelen = strlen ($ rndstring );
// Create an image and set the background color
$ Im = imagecreate (46,20 );
ImageColorAllocate ($ im, 240,243,248 );
// Interference line
$ LineColor1 = ImageColorAllocate ($ im, mt_rand (174,218), mt_rand (190,225), mt_rand (217,237 ));
For ($ j = 1; $ j <= 2; $ j = $ j + 3)
{
Imageline ($ im, 0, $ j + mt_rand (1, 15), 48, $ j + mt_rand (1, 15), $ lineColor1 );
}
// Output text
$ FontColor = ImageColorAllocate ($ im, mt_rand (0,150), mt_rand (0,150), mt_rand (0,150 ));
For ($ I = 0; $ I <$ rndcodelen; $ I ++)
{
$ Bc = mt_rand (0, 1 );
$ Rndstring [$ I] = strtoupper ($ rndstring [$ I]);
Imagestring ($ im, mt_rand (3, 5), $ I * $ img_height/4 + mt_rand (1, 5), mt_rand (1, $ img_width/2), $ rndstring [$ I], $ fontColor );
}
Header ("Pragma: no-cache" r "n ");
Header ("Cache-Control: no-cache" r "n ");
Header ("Expires: 0" r "n ");
// Output a specific image format with a priority of gif-> jpg-> png
If (function_exists ("imagepng "))
{
Header ("content-type: image/png" r "n ");
Imagepng ($ im );
}
Else
{
Header ("content-type: image/jpeg" r "n ");
Imagejpeg ($ im );
}
ImageDestroy ($ im );
Exit ();
}
Else
{
// GD is not supported. only the English letter ABCD is output.
$ _ SESSION ['DD _ ckstr'] = "abcd ";
$ _ SESSION ['DD _ ckstr_last '] = '';
Header ("content-type: image/png" r "n ");
Header ("Pragma: no-cache" r "n ");
Header ("Cache-Control: no-cache" r "n ");
Header ("Expires: 0" r "n ");
$ Fp = fopen ("data/vdcode.jpg", "r ");
Echo fread ($ fp, filesize ("data/vdcode.jpg "));
Fclose ($ fp );
Exit ();
}
?>