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How to implement PHP login verification code

藏色散人Original: 2019-10-16 10:09:343180browse

How to implement php login verification code?

1. Let’s first create an html page to display the verification code

<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <title>登陆</title>
</head>
<body>
    <form action="./login.php" method="post">
        <img src="image_captcha.php"  onclick="this.src=&#39;image_captcha.php?&#39;+new Date().getTime();" width="200" height="200"><br/>
        <input type="text" name="captcha" placeholder="请输入图片中的验证码"><br/>
        <input type="submit" value="验证">
    </form>
</body>
</html>

2. Create a PHP file and accept the verification code information passed in from the front-end page

<?php
/**
 * 接受用户登陆时提交的验证码
 */
session_start();
//1. 获取到用户提交的验证码
$captcha = $_POST["captcha"];
//2. 将session中的验证码和用户提交的验证码进行核对,当成功时提示验证码正确，并销毁之前的session值,不成功则重新提交
if(strtolower($_SESSION["captchaimg"]) == strtolower($captcha)){
    echo "验证码正确!";
    $_SESSION["captcha"] = "";
}else{
    echo "验证码提交不正确!";
}

3. Create a verification code to generate a PHP file

<?php
/**
 * 字母+数字的验证码生成
 */
// 开启session
session_start();
//1.创建黑色画布
$image = imagecreatetruecolor(100, 30);
 
//2.为画布定义(背景)颜色
$bgcolor = imagecolorallocate($image, 255, 255, 255);
 
//3.填充颜色
imagefill($image, 0, 0, $bgcolor);
 
// 4.设置验证码内容
 
//4.1 定义验证码的内容
$content = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
 
//4.1 创建一个变量存储产生的验证码数据，便于用户提交核对
$captcha = "";
for ($i = 0; $i < 4; $i++) {
    // 字体大小
    $fontsize = 10;
    // 字体颜色
    $fontcolor = imagecolorallocate($image, mt_rand(0, 120), mt_rand(0, 120), mt_rand(0, 120));
    // 设置字体内容
    $fontcontent = substr($content, mt_rand(0, strlen($content)), 1);
    $captcha .= $fontcontent;
    // 显示的坐标
    $x = ($i * 100 / 4) + mt_rand(5, 10);
    $y = mt_rand(5, 10);
    // 填充内容到画布中
    imagestring($image, $fontsize, $x, $y, $fontcontent, $fontcolor);
}
$_SESSION["captcha"] = $captcha;
 
//4.3 设置背景干扰元素
for ($$i = 0; $i < 200; $i++) {
    $pointcolor = imagecolorallocate($image, mt_rand(50, 200), mt_rand(50, 200), mt_rand(50, 200));
    imagesetpixel($image, mt_rand(1, 99), mt_rand(1, 29), $pointcolor);
}
 
//4.4 设置干扰线
for ($i = 0; $i < 3; $i++) {
    $linecolor = imagecolorallocate($image, mt_rand(50, 200), mt_rand(50, 200), mt_rand(50, 200));
    imageline($image, mt_rand(1, 99), mt_rand(1, 29), mt_rand(1, 99), mt_rand(1, 29), $linecolor);
}
 
//5.向浏览器输出图片头信息
header(&#39;content-type:image/png&#39;);
 
//6.输出图片到浏览器
imagepng($image);
 
//7.销毁图片
imagedestroy($image);

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