Simple implementation of Chinese verification code with php combined with GD library

I wrote a common verification code last time, now play with the Chinese verification code, and upgrade the code written by the way. The
process is basically the same

First look at whether the GD library is turned on
Generate Chinese 5-digit verification code
Start drawing
Draw interferon
Generate graphics
Finished

Generate Chinese verification code

//小小心机
$hanzi= "如果觉得写得还可以的话互相关注报团取暖交流经验小码农巴拉啊鹏哦溜要了吗不能把呗日无一人说的回复看介绍请问惹锐欧尼之额心想城型从不错框架铝合金";
//获取中文字符的最大索引号
$c = mb_strlen($hanzi)-1;
//var_dump($c);
for($i = 0;$i < 5;$i++){
    
    
	//获取起始点
    $start = rand(0,$c);
    //循环取出一个汉字
    $code.= mb_substr($hanzi,$start,1);
}

It can be clearly seen that a Chinese character occupies 3 bytes, and a Chinese character in UTF-8 encoding format occupies 3 bytes

Draw!

$img = imagecreate(120,30);

$white = imagecolorallocate($img,255,255,255);
$black = imagecolorallocate($img,0,0,0);
//点干扰素
for ($i = 0;$i< 200;$i++) {
    
    
//这里的颜色我就用随机产生的颜色了，之前是给定好了的    
imagesetpixel($img,rand(0,120),rand(0,30),imagecolorallocate($img,rand(0,255),rand(0,255),rand(0,255)));
}
//线干扰素
for($i = 0;$i<20;$i++){
    
    
//这里的颜色我就用随机产生的颜色了，之前是给定好了的
imageline($img,rand(0,120),rand(0,30),rand(0,120),rand(0,30),imagecolorallocate($img,rand(0,255),rand(0,255),rand(0,255)));
}

//像素字体大小
$size = 16;
//角度大小

$fontfile = "simhei.ttf";

//获取文本范围，见下方图
$info=imagettfbbox($size,rand(0,5),$fontfile,$code);
//echo '<pre>';
//print_r($info);
$code_w=$info[4]-$info[6];	//字符串的宽度
$code_h=$info[1]-$info[7];	//字符串的高度
//imagesx($img)  image 所代表的图像的宽度
$x=(imagesx($img)-$code_w)/2;	//起始点的$x
$y=(imagesy($img)+$code_h)/2;	//起始点的$y
//向图像写入文本
imagettftext($img,$size,rand(0,5),$x,$y,imagecolorallocate($img,rand(0,255),rand(0,255),rand(0,255)),$fontfile,$code);
//生成图像
imagejpeg($img);

imagedestroy($img);

Here $info is an array (you can take a look at print_r()). Each item in the array actually corresponds to a coordinate. Imagesx( $img) is the width of the image represented by the image, so I want to keep the Chinese characters as much as possible Place it in the center of the picture, otherwise it will be off and invisible Insert picture description here

Generate verification code

Small example

<?php

session_start();
header("content-type:text/html;chartset:utf-8");
echo '<pre>';
var_dump($_SESSION);
var_dump($_POST);
echo '</pre>';
if($_SESSION['code'] == $_POST['code']){
    
    
    echo '验证成功';
    //进行后续操作balabala
}
?>
<!doctype html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport"
          content="width=device-width, user-scalable=no, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
</head>
<body>
<form action="" method="post">
    <input type="text" name="code" placeholder="">
    <!-- 开始做简单的验证-->
    <img src="index.php" onclick="this.src='index.php?'+Math.random()" alt="">
    <input type="submit" value="提交">
</form>
</body>
</html>

Do verification