Tutorial on writing a pure digital verification code in PHP-PHP Tutorial-php.cn

Tutorial on writing a pure digital verification code in PHP

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Release： 2023-03-11 07:28:01

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Now let’s talk about the simple pure digital verification code.

If you are a beginner, it is recommended to follow the comments //numbers of my code step by step. The easiest way is to copy the entire code.

Create a new captcha.php:

<?php  //11>设置session,必须处于脚本最顶部  session_start();     
/*$image = imagecreatetruecolor(100, 30);    
//1>设置验证码图片大小的函数  
//5>设置验证码颜色 imagecolorallocate(int im, int red, int green, int blue);  
$bgcolor = imagecolorallocate($image,255,255,255); //#ffffff  
//6>区域填充 int imagefill(int im, int x, int y, int col) (x,y) 所在的区域着色,col 表示欲涂上的颜色  imagefill($image, 0, 0, $bgcolor);  //10>设置变量  $captcha_code = "";*/        
//7>生成随机数字  for($i=0;$i<4;$i++){    //设置字体大小    $fontsize = 6;        //设置字体颜色，随机颜色    $fontcolor = imagecolorallocate($image, rand(0,120),rand(0,120), rand(0,120));      
//0-120深颜色    //设置数字    $fontcontent = rand(0,9);    //10>.=连续定义变量    $captcha_code .= $fontcontent;      //设置坐标    $x = ($i*100/4)+rand(5,10);    $y = rand(5,10);     
imagestring($image,$fontsize,$x,$y,$fontcontent,$fontcolor);  }  //10>存到session  $_SESSION[&#39;authcode&#39;] = $captcha_code;  //8>增加干扰元素，设置雪花点  for($i=0;$i<200;$i++){    
//设置点的颜色，50-200颜色比数字浅，不干扰阅读    $pointcolor = imagecolorallocate($image,rand(50,200), rand(50,200), rand(50,200));        
//imagesetpixel — 画一个单一像素    imagesetpixel($image, rand(1,99), rand(1,29), $pointcolor);  }  //9>增加干扰元素，设置横线  for($i=0;$i<4;$i++){    //设置线的颜色    
$linecolor = imagecolorallocate($image,rand(80,220), rand(80,220),rand(80,220));    //设置线，两点一线    imageline($image,rand(1,99), rand(1,29),rand(1,99), rand(1,29),$linecolor);  }   
//2>设置头部，image/png  header(&#39;Content-Type: image/png&#39;);  //3>imagepng() 建立png图形函数  imagepng($image);  //4>imagedestroy() 结束图形函数 销毁$image  imagedestroy($image);
 
接着就是静态页的代码了：index.html
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional
//EN" "、www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns=" 
<head><meta http-equiv="Content-Type" content="text/html; charset=utf-8" /><title>无标题文档</title>
</head><body><form method="post" action="./form.php">  
<p>验证码: <img id="captcha_img" border=&#39;1&#39; src=&#39;./captcha.php?r=echo rand(); ?>&#39; style="width:100px; height:30px" />    
<a href="javascript：void(0)" onclick="document.getElementById(&#39;captcha_img&#39;).src=&#39;./captcha.php?r=&#39;+Math.random()">换一个?</a>  </p>  <P>请输入验证码:<input type="text" name=&#39;authcode&#39; value=&#39;&#39;/></p>  <p><input type=&#39;submit&#39; value=&#39;提交&#39; style=&#39;padding:6px 5px;&#39;/></p></form></body></html>
从index.html可以看到，提交的表单是到form.php的，所以还要有一个判断的form.php代码：
<?php  header("Content-Type:text/html;charset=utf-8");      
//设置头部信息  //isset()检测变量是否设置  if(isset($_REQUEST[&#39;authcode&#39;])){    
session_start();    //strtolower()小写函数    if(strtolower($_REQUEST[&#39;authcode&#39;])== $_SESSION[&#39;authcode&#39;]){      
//跳转页面      echo "<script language=\"javascript\">";      echo "document.location=\"./form.php\"";      
echo "</script>";    }else{      //提示以及跳转页面      echo "<script language=\"javascript\">";      
echo "alert(&#39;输入错误!&#39;);";      echo "document.location=\"./form.php\"";      echo "</script>";    }    
exit(); 
 }

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