Randomly generate verification codes using addition and subtraction algorithms

This time I will bring you a verification code that randomly generates a verification code using the addition and subtraction algorithm. What are the precautions for randomly generating the verification code using the addition and subtraction algorithm. The following is a practical case, let’s take a look.

This is a demo I found online, and I added part of the code. can use.

It needs to be explained here that when we call this verification code class, it should be used in a separate controller method.

The algorithm of the generated image is generated by code, and then the calculated value is stored in the session.

When verifying, the user’s input value is obtained, and then the value on the server is taken out for comparison.

<?php 
namespace mobile\components;
/** 
 * @author fenghuo 
 * 
 * 改造的加减法验证类 
 * 使用示例 VerifyCode::get(1,2); 
 * 验证示例 VerifyCode::check($code); 
 */ 
class VerifyCode 
{ 
  /** 
   * php验证码 
   */ 
  public static function get($one,$two,$prefix = &#39;&#39;, $font_size = 28) 
  { 
    //文件头... 
    ob_get_clean();
    header("Content-type: image/png;charset=utf-8;"); 
    //创建真彩色白纸 
    $width      = $font_size*5; 
    $height      = $font_size+1; 
    $im        = @imagecreatetruecolor($width, $height) or die("建立图像失败"); 
    //获取背景颜色 
    $background_color = imagecolorallocate($im, 255, 255, 255); 
    //填充背景颜色 
    imagefill($im, 0, 0, $background_color); 
    //获取边框颜色 
    $border_color   = imagecolorallocate($im, 200, 200, 200); 
    //画矩形，边框颜色200,200,200 
    imagerectangle($im,0,0,$width - 1, $height - 1,$border_color); 
    //逐行炫耀背景，全屏用1或0 
    for($i = 2;$i < $height - 2;$i++) { 
      //获取随机淡色 
      $line_color = imagecolorallocate($im, rand(200,255), rand(200,255), rand(200,255)); 
      //画线 
      imageline($im, 2, $i, $width - 1, $i, $line_color); 
    } 
    //设置印上去的文字 
    $firstNum = $one; 
    $secondNum = $two; 
    $actionStr = $firstNum > $secondNum ? '-' : '+'; 
    //获取第1个随机文字 
    $imstr[0]["s"] = $firstNum; 
    $imstr[0]["x"] = rand(2, 5); 
    $imstr[0]["y"] = rand(1, 4); 
    //获取第2个随机文字 
    $imstr[1]["s"] = $actionStr; 
    $imstr[1]["x"] = $imstr[0]["x"] + $font_size - 1 + rand(0, 1); 
    $imstr[1]["y"] = rand(1,5); 
    //获取第3个随机文字 
    $imstr[2]["s"] = $secondNum; 
    $imstr[2]["x"] = $imstr[1]["x"] + $font_size - 1 + rand(0, 1); 
    $imstr[2]["y"] = rand(1, 5); 
    //获取第3个随机文字 
    $imstr[3]["s"] = '='; 
    $imstr[3]["x"] = $imstr[2]["x"] + $font_size - 1 + rand(0, 1); 
    $imstr[3]["y"] = 3; 
    //获取第3个随机文字 
    $imstr[4]["s"] = '?'; 
    $imstr[4]["x"] = $imstr[3]["x"] + $font_size - 1 + rand(0, 1); 
    $imstr[4]["y"] = 3; 
    //文字 
    $text = ''; 
    //写入随机字串 
    for($i = 0; $i < 5; $i++) { 
      //获取随机较深颜色 
      $text_color = imagecolorallocate($im, rand(50, 180), rand(50, 180), rand(50, 180)); 
      $text .= $imstr[$i]["s"]; 
      //画文字 
      imagechar($im, $font_size, $imstr[$i]["x"], $imstr[$i]["y"], $imstr[$i]["s"], $text_color); 
    } 
    session_start();
    $_SESSION[$prefix.&#39;verifycode&#39;] = $firstNum > $secondNum ? ($firstNum - $secondNum) : ($firstNum + $secondNum); 
    //显示图片 
    ImagePng($im); 
    //销毁图片 
    ImageDestroy($im); 
  } 
  public static function check($code) 
  { 
    if(trim($_SESSION[$prefix.'verifycode']) == trim($code)) { 
      return true; 
    } else { 
      return false; 
    } 
  } 
}

I believe you have mastered the method after reading the case in this article, and there will be more exciting things. Please pay attention to other related articles on php Chinese website!

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