PHP中GD函数生成动态随机验证码

古城热线

<?php
$rand_num =rand();
$str = md5($rand_num);
$num_code=5;
//截取随机码
$str_code = substr($str, 0,$num_code);
//画布大小
$width = 60;
$height =25;
//创建图片句柄
$image = imagecreate($width, $height);
//背景颜色
$bg_color =imagecolorallocate($image, 255, 255, 255);
//边框色
$border_color =imagecolorallocate($image, 0, 0, 0);
//绘制边框
imagerectangle($image, 0, 0, $width-1, $height-1, $border_color);
for ($i = 0; $i < $num_code; $i++) {
//随机产生验证码颜色
$str_color = imagecolorallocate($image, rand(0,255), rand(0,255), rand(0,255));
//字体颜色
$font_size = 10;
//设置验证码位置
$str_x=floor(($width/$num_code)*$i)+rand(0,5);
$str_y =rand(2, $height-15);
//将随机码添加到画布上,每个随即字符都不同颜色大小
imagechar($image, $font_size, $str_x, $str_y, $str_code[$i], $str_color);
}
header("content-type:image/png");
//显示图片
imagepng($image);
//释放资源
imagedestroy($image);
　　?>