PHP verification code PHP non-preset image generates verification code

This article introduces the method of generating verification codes from PHP non-preset images. There is no need to preset the verification code images in the server in advance. The picture background is drawn randomly. For examples of generating verification codes, friends in need can refer to it.

php generate verification code

php generates a separate page for the verification code. There is no need to preset the verification code image in the server in advance. The picture background is drawn randomly. Topic recommendation: PHP verification code collection At any page location where the verification code needs to be displayed, use the tag to load the access address of the file. The server-side verification code value is stored in the session: $_SESSION['randcode']

Full code:

<?php
Header("Content-type: image/gif");
/*
* 初始化
*/
$border = 0; //是否要边框 1要:0不要
$how = 4; //验证码位数
$w = $how*30; //图片宽度
$h = 40; //图片高度
$fontsize = 5; //字体大小，默认只有1、2、3、4、5 五个大小，如需其他，参照imageloadfont() 函数
$alpha = "abcdefghijkmnopqrstuvwxyz"; //验证码内容1:字母
$number = "023456789"; //验证码内容2:数字
$randcode = ""; //验证码字符串初始化
srand((double)microtime()*1000000); //初始化随机数种子
 
$im = ImageCreate($w, $h); //创建验证图片
 
/*
* 绘制基本框架
*/
$bgcolor = ImageColorAllocate($im, 255, 255, 255); //设置背景颜色
ImageFill($im, 0, 0, $bgcolor); //填充背景色
if($border)
{
    $black = ImageColorAllocate($im, 0, 0, 0); //设置边框颜色
    ImageRectangle($im, 0, 0, $w-1, $h-1, $black);//绘制边框
}
 
/*
* 逐位产生随机字符
*/
for($i=0; $i<$how; $i++)
{   
    $alpha_or_number = mt_rand(0, 1); //字母还是数字
    $str = $alpha_or_number ? $alpha : $number;
    $which = mt_rand(0, strlen($str)-1); //取哪个字符
    $code = substr($str, $which, 1); //取字符
    $j = !$i ? 4 : $j+15; //绘字符位置
    $color3 = ImageColorAllocate($im, mt_rand(0,100), mt_rand(0,100), mt_rand(0,100)); //字符随即颜色
    ImageChar($im, $fontsize, $j, 3, $code, $color3); //绘字符
    $randcode .= $code; //逐位加入验证码字符串
}
 
/*
* 添加干扰
*/
for($i=0; $i<5; $i++)//绘背景干扰线
{   
    $color1 = ImageColorAllocate($im, mt_rand(0,255), mt_rand(0,255), mt_rand(0,255)); //干扰线颜色
    ImageArc($im, mt_rand(-5,$w), mt_rand(-5,$h), mt_rand(20,300), mt_rand(20,200), 55, 44, $color1); //干扰线
}   
for($i=0; $i<$how*40; $i++)//绘背景干扰点
{   
    $color2 = ImageColorAllocate($im, mt_rand(0,255), mt_rand(0,255), mt_rand(0,255)); //干扰点颜色 
    ImageSetPixel($im, mt_rand(0,$w), mt_rand(0,$h), $color2); //干扰点
}
 
//把验证码字符串写入session
session_start();
$_SESSION['randcode'] = $randcode;
 
/*绘图结束*/
Imagegif($im);
ImageDestroy($im);
/*绘图结束*/
?>