一个非常简单的PHP验证码生成例子，在这个PHP验证码生成我们需要使用到php_gd2.dll扩展了，下面我就来给大家整个例子了，希望对各位朋友会带来帮助哦。
使用PHP的GD库扩展类制作验证码的基本步骤：
启用php.ini配置文件中的extension=php_gd2.dll扩展（打开php.ini配置文件，去掉行首的分号后重启Apache即可）；
下面是PHP生成验证码的代码：
<?php
for($i=0;$i<5;$i++){
$suijishu.=dechex(rand(1,15));//使用循环产生一个十六进制格式的五位数
}
setcookie("useryzm",$suijishu);//创建一个名为useryzm、值为$suijishu的cookie
$img=imagecreatetruecolor(100,30);//创建一个宽100高30的图片验证码
$bg=imagecolorallocate($img,rand(0,255),rand(0,255),rand(0,255));//定义验证码的背景颜色
$sc=imagecolorallocate($img,rand(0,255),rand(0,255),rand(0,255));//定义验证码字体的颜色
imagestring($img,5,rand(0,50),rand(0,15),$suijishu,$sc);//定义字体的位置（左上角为坐标原点）
for($k=0;$k<10;$k++){
imageline($img,rand(1,100),rand(1,100),rand(1,100),rand(1,100),$sc);//在验证码上绘制直线（扰乱作用）
imagesetpixel($img,rand(1,100),rand(1,30),$sc);//在验证码上绘制点（扰乱作用）
}
ob_clean();//清空输出缓冲区（这句很重要）
header("Content-type:image/jpeg");//定义输出图片的格式（image/后面可以是jpeg或png或gif等图片格式）
imagejpeg($img);//输出图象
imageDestroy($img);//释放内存，完成创建
?>下面是HTML中调用验证码的代码：
<html>
...
<script language="javascript">
function changeyzm(){
var img = document.getElementById("yzmimg").src = "gdyzm.php?id="+Math.random()*10;
return ;
}
</script>
...
<img src="/static/imghwm/default1.png" data-src="gdyzm.php" class="lazy" name="yzmimg" style="max-width:90%" style="max-width:90%" id="yzmimg" title="点击刷新" onclick="changeyzm();" / alt="PHP验证码生成例子 " >
...
</html>如果出现"图像“XXXX”因其本身有错无法显示"的错误，很可能是漏了ob_clean();这句，或是文件的物理编码出了问题（修改物理编码的方法可以参考PHP创建utf8文件）
如果没有加ob_clean();这句，在本地测试且物理编码为ANSI时没问题，物理编码为UTF-8时则会报错（图像“XXXX”因其本身有错无法显示）
教程链接:
随意转载~但请保留教程地址★
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