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How to do verification code in php

(*-*)浩Original: 2019-09-27 10:57:213166browse

PHP verification code production is an assessment of basic PHP skills. PHP verification code production must open the gd library, because many functions in the gd library are used

Process the image according to the GD library in php, draw the picture of the verification code,

form interface in code.php, simple session saving and comparison with user input, confirm Whether the verification is correct, in form.php (recommended learning: PHP programming from entry to proficiency)

<?php
    session_start();//必须位于脚本的最顶端
   $image=imagecreatetruecolor(100, 30);//imagecreatetruecolor函数建一个真彩色图像
   //生成彩色像素    
   $bgcolor=imagecolorallocate($image, 255, 255, 255);//白色背景     imagecolorallocate函数为一幅图像分配颜色
   $textcolor=imagecolorallocate($image,0,0,255);//蓝色文本
   //填充函数，xy确定坐标，color颜色执行区域填充颜色
   imagefill($image, 0, 0, $bgcolor);
   $captch_code="";//初始空值

   //该循环,循环取数
   for($i=0;$i<4;$i++){
     $fontsize=6;
     $x=($i*25)+rand(5,10);
     $y=rand(5,10);//位置随机
    //  $fontcontent=$i>2?chr(rand(97,122)):chr(rand(65,90));//是小写，否则是大写
    $data=&#39;abcdefghijkmnpqrstuvwxyz3456789&#39;;
    $fontcontent=substr($data,rand(0,strlen($data)-1),1);//strlen仅仅是一个计数器的工作  含数字和字母的验证码
                                                           //可以理解为数组长度0到30

 $fontcolor=imagecolorallocate($image,rand(0,100),rand(0,100),rand(0,100));//随机的rgb()值可以自己定

    imagestring($image,$fontsize,$x,$y,$fontcontent,$fontcolor); //水平地画一行字符串
    $captch_code.=$fontcontent;
}
    $_SESSION[&#39;authcode&#39;]=$captch_code;//将变量保存再session的authcode变量中

    
    //该循环,循环画背景干扰的点
    for($m=0;$m<=600;$m++){

     $x2=rand(1,99);
     $y2=rand(1,99);
     $pointcolor=imagecolorallocate($image,rand(0,255),rand(0,255),rand(0,255));
    imagesetpixel($image,$x2,$y2,$pointcolor);// 水平地画一串像素点
    }

    //该循环,循环画干扰直线
   for ($i=0;$i<=10;$i++){
       $x1=rand(0,99);
       $y1=rand(0,99);
       $x2=rand(0,99);
       $y2=rand(0,99);
       $linecolor=imagecolorallocate($image,rand(0,255),rand(0,255),rand(0,255));
       imageline($image,$x1,$y1,$x2,$y2,$linecolor);//画一条线段
   
   }
   header(&#39;content-type:image/png&#39;);
   imagepng($image);
   //销毁
   imagedestroy($image);
?>

Code:

<?php
// session 存值并匹配用户输入值
    if (isset($_REQUEST[&#39;authcode&#39;])) {
        session_start();
        if (strtolower($_REQUEST[&#39;authcode&#39;])==$_SESSION[&#39;authcode&#39;]) {//strtolower转化为小写的函数
            echo"输入正确！";
            # code...
        }
        else{
            echo"输入错误！";
        }
        exit();
    }
?>
<!DOCTYPE html>
<html>
<head>
<!-- 简单的表单提交代码 -->
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>简单验证码的实现</title>
</head>
<body>
    <form method="post" action="./form.php">
    <p>验证码图片:<img src="code.php" onClick="this.src=&#39;code.php?nocache=&#39;+Math.random()" style="cursor:hand" alt="点击换一张"/>点击图片可更换验证码</p>
    <p>请输入图片中的内容:<input type="text" name="authcode" value=""/></p>
    <p><input type="submit" width="20px" height=19px value="提交"></input></p>
    </form>
    
</body>
</html>

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