Detailed explanation of how PHP implements operable verification codes

How does PHP implement operable verification codes? This article mainly introduces how to implement operable verification codes in PHP. The code is very detailed and worth learning. Interested friends can refer to it. I hope to be helpful.

This article shares a code example of implementing a computable verification code in PHP. I hope it will be helpful to everyone's learning.

demo.php code

<?php 
session_start(); 
if(!emptyempty($_POST[&#39;Login&#39;])){ 
  if(md5(strtoupper($_POST[&#39;Login&#39;])) == $_SESSION[&#39;Login&#39;]){ 
    echo &#39;Correct&#39;; 
  }else{ 
    echo &#39;Error&#39;;   
  } 
} 
?> 
 
<form method="post"> 
  <input type="text" name="Login" value="" /><img src="img.php?Action=Login&imgW=80&imgH=30" align="absmiddle"> 
  <input type="submit" value="Login" /> 
</form>

img.php code

<?php 
session_start(); 
function getCode ($length = 32, $mode = 0) 
{ 
switch ($mode) 
{ 
   case &#39;1&#39;: 
     $str = &#39;123456789&#39;; 
      break; 
 case &#39;2&#39;: 
      $str = &#39;abcdefghijklmnopqrstuvwxyz&#39;; 
      break; 
 case &#39;3&#39;: 
      $str = &#39;ABCDEFGHIJKLMNOPQRSTUVWXYZ&#39;; 
      break; 
 case &#39;4&#39;: 
      $str = &#39;ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz&#39;; 
      break; 
 case &#39;5&#39;: 
      $str = &#39;ABCDEFGHIJKLMNPQRSTUVWXYZ123456789&#39;; 
      break; 
    case &#39;6&#39;: 
      $str = &#39;abcdefghijklmnopqrstuvwxyz1234567890&#39;; 
      break; 
    default: 
      $str = &#39;ABCDEFGHIJKLMNPQRSTUVWXYZabcdefghijkmnpqrstuvwxyz23456789&#39;; 
      break; 
} 
 
$result = &#39;&#39;; 
$l = strlen($str)-1; 
for($i = 0;$i < $length;$i ++) 
{ 
 $num = rand(0, $l); 
 $result .= $str[$num]; 
} 
return $result; 
} 
//建立验证图片 
function createAuthNumImg($randStr,$imgW=100,$imgH=40,$fontName) 
{ 
header ("content-type: image/png"); 
$image = imagecreate($imgW , $imgH); 
$color_white = imagecolorallocate($image , 255 , 255 , 255); 
$color_gray = imagecolorallocate($image , 228 , 228 , 228); 
$color_black = imagecolorallocate($image , 255 , 102 , 204); 
for ($i = 0 ; $i < 1000 ; $i++) 
{ 
 imagesetpixel($image , mt_rand(0 , $imgW) , mt_rand(0 , $imgH) , $color_gray); 
} 
imagerectangle($image , 0 , 0 , $imgW - 1 , $imgH - 1 , $color_gray); 
for ($i=10;$i<$imgH;$i+=10) 
 imageline($image, 0, $i, $imgW, $i, $color_gray); 
imagettftext($image,16,5,3,25,$color_black,$fontName,$randStr); 
for ($i=10;$i<$imgW;$i+=10) 
 imageline($image, $i, 0, $i, $imgH, $color_gray); 
imagepng($image); 
imagedestroy($image); 
} 
 
$a=GetCode(1,1); 
$b=GetCode(1,1); 
$c=GetCode(1,1); 
$Passport=$a."+".$b."+".$c; 
$Total=$a+$b+$c; 
$Total; 
$_SESSION[$_GET[&#39;Action&#39;]]=md5(strtoupper($Total)); 
createAuthNumImg($Passport,$_GET[&#39;imgW&#39;],$_GET[&#39;imgH&#39;],"verdana.ttf"); 
?>

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