1、开始之前首先安装php开发环境，这里使用xampp
2、打开php的gd2图形库支持（在php.ini,中搜索“php_gd2.dll”，找到“;extension=php_gd2.dll”并去掉句首的分号） 。http://127.0.0.1/dashboard/phpinfo.php
3、表明已经安装了gd库。核心：img.php
4、这个页面生成一张验证艨位雅剖码并将正确数值写入Session随机一个4位验证码$check=rand(1000,9999);将生成的验证码写入sessionSession_start();$_SESSION[‘check’]=$check;创建一张图片$im = imagecreate(80,30);由于这种图片的背景默认是黑色的所以我们要用白色填充。Imagefill($im,0,0,ImageColorAllocate($im,255,255,255));使用imageline随机绘制两条实线$y1=rand(0,30);$y2=rand(0,30);$y3=rand(0,30);$y4=rand(0,30);imageline($im,0,$y1,70, $y3,000);imageline($im,0,$y2,70, $y4,000);在随机位置绘制文字$strx=rand(3,15);$stry=rand(2,15);imagestring($img,5,$strx,$stry,substr($check,0,1),ImageColorAllocate($img,34,87,100));$strx+=rand(15,20);$stry=rand(2,15);imagestring($img,5,$strx,$stry,substr($check,1,1),ImageColorAllocate($img,781,117,78));$strx+=rand(15,20);$stry=rand(2,15);imagestring($img,5,$strx,$stry,substr($check,2,1),ImageColorAllocate($img,160,40,40));$strx+=rand(15,20);$stry=rand(2,15);imagestring($img,5,$strx,$stry,substr($check,3,1),ImageColorAllocate($img,25,55,10));输出图像Header("Content-type: image/PNG");ImagePNG($img);结束，下面是完整代码<?php $check=rand(1000,9999);Session_start(); $_SESSION["check"] = $check; $img = imagecreate(80,30); imagefill($img,0,0,ImageColorAllocate($img,255,255,255)); $y1=rand(0,30); $y2=rand(0,30); $y3=rand(0,30); $y4=rand(0,30); imageline($img,0,$y1,70, $y3,ImageColorAllocate($img,55,255,25)); imageline($img,0,$y2,70, $y4,ImageColorAllocate($img,55,55,255)); $strx=rand(3,15); $stry=rand(2,15); imagestring($img,5,$strx,$stry,substr($check,0,1),ImageColorAllocate($img,34,87,100)); $strx+=rand(15,20);$stry=rand(2,15); imagestring($img,5,$strx,$stry,substr($check,1,1),ImageColorAllocate($img,781,117,78)); $strx+=rand(15,20);$stry=rand(2,15); imagestring($img,5,$strx,$stry,substr($check,2,1),ImageColorAllocate($img,160,40,40)); $strx+=rand(15,20);$stry=rand(2,15); imagestring($img,5,$strx,$stry,substr($check,3,1),ImageColorAllocate($img,25,55,10)); Header("Content-type: image/PNG"); ImagePNG($img);上边是img.php代码
5、用户界面：index.php<!DOCTYPE html><html><body><稆糨孝汶;form action="action.php" method="post"><input type="text" name="cikle" placeholder="验证码"><br><img id="cikle" style="-webkit-user-select: none" src="img.php"><input type="submit" value="Submit"></form></body></html>
6、检查：action.php这一步要将用户输入数值与session中的数值进行比对相等，输出“正确”不相等，输出“不正确”<?phpSession_start(); if ($_SERVER["REQUEST_METHOD"] == "POST") {if($_SESSION["check"]!=intval($_POST["cikle"])){echo "不正确";}else{echo "正确";}}
7、如果错误，会输出不正确
