Detailed generation and use of php verification code_PHP tutorial

Note: The following code requires opening the gd library of the php tutorial, modifying the configuration of the php.in file, and canceling the semicolon before the commented out line: extension=php_gd2.dll.

$width = 165;
$height = 120;
         $image = imagecreatetruecolor($width,$height);
$bg_color = imagecolorallocate($image,255,255,255);
          $tm = imagecolorallocate($image,255,0,0);
Imagefilledrectangle($image,0,0,$width,$height,$bg_color);
Imagefill($image,0,0,$bg_color);
          /*
​​​​ //$text = random_text(5);
          $text = "ffff";
$font = 8;
          $struft=iconv("gbk","utf-8",$text);
          $x = imagesx($image);
          $y = imagesy($image);
          $fg_color = imagecolorallocate($image,233,14,91);
Imagestring($image,$font,$x,$y,$struft,$fg_color);
          $_session['captcha'] = $text;
*/
header("content-type:image/png");
Imagepng($image);
         imagedestroy($image);

Example 2

validate.php

Adopts session recognition, slightly improved the PHP verification code currently circulating on the Internet, added miscellaneous dots, randomly displayed numbers and colors, and controlled 4-digit display;

session_start();
//Generate verification code image
header("content-type: image/png");
$im = imagecreate(44,18);
$back = imagecolorallocate($im, 245,245,245);
imagefill($im,0,0,$back); //Background

srand((double)microtime()*1000000);
//Generate 4-digit number
for($i=0;$i<4;$i++){
$font = imagecolorallocate($im, rand(100,255),rand(0,100),rand(100,255));
$authnum=rand(1,9);
$vcodes.=$authnum;
imagestring($im, 5, 2+$i*10, 1, $authnum, $font);
}

for($i=0;$i<100;$i++) //Add interference pixels
{
$randcolor = imagecolorallocate($im,rand(0,255),rand(0,255),rand(0,255));
imagesetpixel($im, rand()%70 , rand()%30 , $randcolor);
}
imagepng($im);
imagedestroy($im);

$_session['vcode'] = $vcodes;
?>

See the complete example below

@header("content-type:text/html; charset=utf-8");

//Open session

session_start();

?>

 

 

Verification code:

 

 

 

 

 

                   Enter the verification code:

                     

 

php determines whether the verification code entered by the user is consistent with the one generated by the system

//Open session

session_start();

//Get the verification code entered by the user and convert it to uppercase

$imgid_req = $_request['imgid'];

$imgid_req = strtoupper($imgid_req);

//Verify whether the string is registered with the session variable

if (session_is_registered($imgid_req)) {

echo "Verified!";

} else {

echo "Verification error!";

}

//Close the session to clear all registered variables

session_destroy();

?>

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