How to use PHP drawing function to implement simple verification code function_php example

<&#63;php
//===================================》》使用绘图技术绘制验证码

//1.随机产生4个随机数
$checkCode="";
for ($i=0;$i<4;$i++){
$checkCode.=dechex(rand(1, 15));// decheck()十进制转换为十六进制,即验证码上要显示的数字
}

//2.存入列
session_start();
$_SESSION['checkCode']=$checkCode;

//3.创建画布
$image1=imagecreatetruecolor(100, 30);

//制造干扰,创建20条弧线
for ($j=0;$j<30;$j++){
imagearc($image1, rand(0, 100), rand(0, 30), rand(0, 100), rand(0, 30), rand(0, 360), rand(0, 360), imagecolorallocate($image1, rand(0, 155), rand(0, 255), rand(0, 255)));
}

//3.创建字体颜色,将字粘贴上去
$white=imagecolorallocate($image1, 255, 255, 255);
imagestring($image1, rand(2, 5), rand(5, 70), rand(2, 15), $checkCode, $white);

//5.输出图像或保存
header("content-type:image/png");
imagepng($image1);

//6.释放资源
imagedestroy($image1);

请输入验证码：<img src="index.php" onclick="this.src='index.php&#63;a=+random()'">