Use PHP to implement the login verification code.

A few days ago saw the DEV-CLUB implementation of the verification code login verification. we implemented it in PHP last night. welcome to discuss with me the principles of polygame@163.net: generate an image and save the characters shown in the image to the SESSION. check whether the entered verification code is the same as the verification code in the SESSION during login. demo address: www. bingdu. netbbs: this is the verification code generated.

A few days ago saw the DEV-CLUB implementation of the verification code login verification. last night in PHP to achieve. welcome everyone and I discuss polygame@163.net

Principle: generate an image and save the characters displayed in the image to the SESSION. when logging in, determine whether the entered verification code is the same as the verification code in the SESSION.
Demo address:

Http://www.bingdu.net/bbs/

This is the checkNumber. php file that generates the verification code and image.

Session_start ();

If ($ act = "init ")
{
Header ("Content-type: image/png ");
Srand (microtime () * 100000 );
$ Login_check_number = strval (rand ("1111", "9999 "));

Session_register ("login_check_number ");
// The SESSION is used to save the verification code.
// You can also use cookies.
// Setcookie ("login_check_number", $ login_check_number );
// Delete session_start () in the first line;
// COOKIE is not recommended because it cannot be used for security verification.

$ H_img = imagecreate (40, 17 );
$ C_black = ImageColorAllocate ($ h_img, 0, 0 );
$ C_white = ImageColorAllocate ($ h_img, 255,255,255 );
Imageline ($ h_img, 1, 1,350, 25, $ c_black );
Imagearc ($ h_img, 200, 15, 20, 20, 35,190, $ c_white );
Imagestring ($ h_img, 5, 2, 1, $ login_check_number, $ c_white );
ImagePng ($ h_img );
ImageDestroy ($ h_img );

Die ();
}
/*
Usage:
Add

Add the following code to the login verification PHP page (note: No output is allowed before the code is added because SESSION is used)

// $ Number indicates the value of the verification code you entered.

Include_once ("./checkNumber. php ");

// Check the verification code

If ($ number! = $ Login_check_number | empty ($ number ))
{
Print ("incorrect verification code! ");
Die ();
}
*/
?>

SESSION usage problems:
If the logon page is opened and the logon fails after the SESSION expires, the logon fails.
COOKIE usage problems:
The COOKIE is stored on the client, so it is better not to use the COOKIE.

For the VBB Forum, save checkNumber. php and modify the template content of the MYSQL database template data table titled logincode forumhome_logincode username_loggedout.
Then in the member. php
If ($ action = "login ")
Add later

// Check the verification code
Include_once ("./checkNumber. php ");
If ($ number! = $ Login_check_number | $ number = "")
{
Print ("incorrect verification code! ");
Die ();
}