PHP Generate Image Verification Code Practice Notes_PHP Tutorial

PHP needs to use the PHP gd library and session to generate a graphical verification code. In this way, the gd library generates pictures for the user to see, and then the user input verification is submitted to the server and the value stored in the session for verification. Let’s take a look at the whole process. Process it.

Windows system GD library is enabled

Find extension=php_gd2.dll in the php.ini file and remove the previous “;”

Linux system GD library is enabled

##Check whether the GD library is installed or not using the command
php5 -m | grep -i gd
Or
php -i | grep -i --color gd
##If the GD library is not installed, install it on the server. The method is as follows
### If it is a source code installation, add the parameter
--with-gd
### If it is a Debian Linux system, use apt-get to install it, as follows
apt-get install php5-gd
### If it is a CentOS system, use yum to install it, as follows
yum install php-gd
### If it is a suse-based Linux system, use yast to install it, as follows
yast -i php5_gd

Okay, the php GD library is ready. Let’s look at an example of php generating a graphic verification code image

First of all, let me introduce to you the simple concept of verification code!

1. Verification code introduction

The verification code is a string of randomly generated numbers or symbols displayed on the page in the form of a picture. The user can identify the verification code information with the naked eye. During the submission operation, the characters on the picture need to be submitted at the same time. A function can only be used after the input submission verification is successful. If the characters submitted are different from those saved in the server session, the submitted information is considered invalid. In order to prevent automatic programs from analyzing and parsing pictures, some interferons are usually randomly generated on the picture or the characters are distorted, making automatic recognition more difficult. After the user submits, the verification code entered by the user is compared with the string saved in the session to achieve the verification effect. When the user submits the form, the page that receives the form checks whether the session generated by the server and the form value submitted by the client are consistent.
Consistent does not read or write to the database. Sessions allow a small amount of user information to be stored on the server; this information is temporary and will be automatically deleted when the user leaves the website.

2. PHP implementation process
PHP web page files are treated as general HTML web page files, and when editing, they can be written using the conventional method of editing HTML. Since PHP consumes very few system resources when used, has open source code, and is free, PHP has been used by more websites now. The following is the process of implementing verification code in PHP:

(1) Generate random numbers
Define the numbers and letters used to display on the image;

Loop and randomly select four defined letters and numbers;
The total number of characters obtained by connecting the numbers is four;
Save the generated numbers and letters, put the generated random numbers in the session variable, and compare them with the content submitted by the user in the future.

The code is as follows	Copy code
代码如下	复制代码
$ aut hnum_session = ' ; ' $ st r = a ' bcdef ghij k l mnopqrstuv wxyz 1234567890 ' ; $ l = strlen( $ str) ; f or( $ i= 1 ; $ i { $ num= rand( 0 , $ l- 1); $ aut hnum_session. = $ str[ $ num];$ aut hnum_session. = $ str[ $ num]; } $ _SESSI ON[ " authnum_ses sion" ] ; ? >

$ aut hnum_session = ' ; '

$ st r = a ' bcdef ghij k l mnopqrstuv wxyz 1234567890 '
;
$ l = strlen( $ str) ;

f or( $ i= 1 ; $ i  代码如下 复制代码 $ i m = i magecreate( 60 , 20);
? > { $ num= rand( 0 , $ l- 1); $ aut hnum_session. = $ str[ $ num];$ aut hnum_session. = $ str[ $ num]; } $ _SESSI ON[ " authnum_ses sion" ] ; ?> (2) Create pictures Use the image creation function to determine the size of the image being created.

The code is as follows	Copy code
$ i m = i magecreate( 60 , 20); ?>

(3) Set color
Use a function to create a background color;
Use functions to create font colors.

The code is as follows

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代码如下	复制代码
$ b lack = ImageColor A ll ocate( $ i m, 0 , 0, 0); $ white = ImageColor A ll ocate( $ i m, 255 , 255 , 255); $ gray = I mageColor A ll ocate ( $ i m , 200 , 200 , 200); i magefill ( $ i m , 68 , 30 , $ gray); $ li = I mageColor A l loca te ( $ i m , 220 , 220 , 220); ? >

$ b lack = ImageColor A ll ocate( $ im, 0 , 0, 0);
$ white = ImageColor A ll ocate( $ im, 255 , 255 ,
255);
$ gray = I mageColor A ll ocate ( $ im , 200 , 200 , 200);

代码如下	复制代码
f or( $ i= 0 ; $ i { i mageline( $ i m , rand ( 0 , 30), rand( 0 , 21), rand( 20 , 40), rand( 0 , 21), $ li ); } f or( $ i= 0 ; $ i { i magesetp i xe l ( $ i m, rand( )% 70 , rand( )% 30 , $ gray); } ? >

i magefill ( $ i m , 68 , 30 , $ gray);

$ li = I mageColor A l loca te ( $ im , 220 , 220 ,
220);
?>

代码如下	复制代码
i magest ring( $ i m, 5 , 12 , 5 , $ au t hnu m _ ses2 sion , $ wh i te); ? >

(4) Add interferon
Without affecting user input, add some interference lines,
interfering pixels.

The code is as follows	Copy code
f or( $ i= 0 ; $ i
代码如下	复制代码
sessi on_start ( ) ; I magePNG( $ i m); ? >

{ i imageline( $ i m , rand ( 0 , 30), rand( 0 , 21), rand( 20 , 40), rand( 0 , 21), $ li ); } f or( $ i= 0 ; $ i { i magesetp i xe l ( $ i m, rand( )% 70 , rand( )% 30 , $ gray); } ?> (5) Write the characters in the upper left corner of the image Use the function i magestring to write characters on the image.

The code is as follows	Copy code
i magest ring( $ i m, 5 , 12 , 5 , $ au t hnu m _ ses2 sion, $ wh i te); ?>

(6) Output image Turn on sessi on function; Use the function to output the image.

The code is as follows	Copy code
sessi on_start ( ) ; I magePNG( $ i m); ?>

The above verification code displays the results as follows

In the page that needs to call the verification code for verification, the user fills in the verification code form, and the system compares the verification code data submitted in the form with the session variable above. If they are equal, the verification is correct and you can continue; No If equal, it is an error, terminating the user's ongoing work and realizing the verification function of the user using the verification code.

Example

Untitled Document

代码如下	复制代码
验证码：       看不清？换一个

The verifycode.php file code is as follows

The code is as follows

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代码如下

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/*   图片验证码 Powered By KASON test http://www.bKjia.c0m   */   session_start();   $num=4;//验证码个数   $width=80;//验证码宽度   $height=20;//验证码高度   $code=' ';   for($i=0;$i   {    switch(rand(0,2))    {     case 0:$code[$i]=chr(rand(48,57));break;//数字     case 1:$code[$i]=chr(rand(65,90));break;//大写字母     case 2:$code[$i]=chr(rand(97,122));break;//小写字母    }   }   $_SESSION["VerifyCode"]=$code;   $image=imagecreate($width,$height);   imagecolorallocate($image,255,255,255);   for($i=0;$i   {    $dis_color=imagecolorallocate($image,rand(0,2555),rand(0,255),rand(0,255));    imagesetpixel($image,rand(1,$width),rand(1,$height),$dis_color);   }   for($i=0;$i   {    $char_color=imagecolorallocate($image,rand(0,2555),rand(0,255),rand(0,255));    imagechar($image,60,($width/$num)*$i,rand(0,5),$code[$i],$char_color);   }   header("Content-type:image/png");   imagepng($image);//输出图像到浏览器   imagedestroy($image);//释放资源 ?>

/*
Image verification code Powered By KASON test http://www.bKjia.c0m */
session_start();
$num=4;//Number of verification codes
$width=80;//Verification code width
$height=20;//Verification code height
$code=' ';
for($i=0;$i {
switch(rand(0,2))
{
Case 0:$code[$i]=chr(rand(48,57));break;//Number
Case 1:$code[$i]=chr(rand(65,90));break;//uppercase letters
Case 2:$code[$i]=chr(rand(97,122));break;//lowercase letters
}
}
$_SESSION["VerifyCode"]=$code;
$image=imagecreate($width,$height);
imagecolorallocate($image,255,255,255);
for($i=0;$i {
$dis_color=imagecolorallocate($image,rand(0,2555),rand(0,255),rand(0,255));
imagesetpixel($image,rand(1,$width),rand(1,$height),$dis_color);
}
for($i=0;$i {
$char_color=imagecolorallocate($image,rand(0,2555),rand(0,255),rand(0,255));
Imagechar($image,60,($width/$num)*$i,rand(0,5),$code[$i],$char_color);
}
header("Content-type:image/png");
imagepng($image);//Output the image to the browser
imagedestroy($image);//Release resources
?>

The checkcode.php file is as follows

The code is as follows

代码如下	复制代码
ini_set('display_errors', 'Off'); session_start();   if((strtoupper($_POST["code"])) == strtoupper(($_SESSION["VerifyCode"]))){  print("验证码正确,");   }else{     print("验证码错误,");   }   echo "提交的验证码:".strtoupper($_POST["code"]).",正确的验证码：".strtoupper($_SESSION["VerifyCode"]); ?>

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ini_set('display_errors', 'Off');
session_start();
if((strtoupper($_POST["code"])) == strtoupper(($_SESSION["VerifyCode"]))){
print("Verification code is correct,");
}else{
Print("Verification code error,");
}
echo "Submitted verification code:".strtoupper($_POST["code"]).", correct verification code: ".strtoupper($_SESSION["VerifyCode"]);
?>

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TechArticle

php needs to use the php gd library and session to generate graphic verification codes, so that the gd library generates pictures for users Look, the user input verification is then submitted to the server and the value stored in the session is verified...