1.验证码代码如下，新建一个含如下代码的PHP文件，此处取名为ValidateCode.php：
<?php /* * ValidateCode.php */ class ValidateCode { private $charset = '0123456789'; private $code; private $codelen = 4; private $width = 163; private $height = 30; private $img; private $font; private $fontsize = 20; private $fontcolor; public function __construct($size) { $this->font = dirname(__file__) . '/t1.ttf'; $this->codelen = $size; $this->charset = str_repeat($this->charset, 4); } private function createCode() { $_len = strlen($this->charset)-1; for ($i=0;$i<$this->codelen;$i++) { $this->code .= $this->charset[mt_rand(0,$_len)]; } } private function createBg() { $this->img = imagecreatetruecolor($this->width , $this->height); $color = imagecolorallocate($this->img, mt_rand(157,255), mt_rand(157,255), mt_rand(157,255)); imagefilledrectangle($this->img, 0, $this->height, $this->width, 0, $color); } private function createFont() { $_x = ($this->width - 10) / $this->codelen; for ($i=0;$i<$this->codelen;$i++) { $this->fontcolor = imagecolorallocate($this->img,mt_rand(0,156),mt_rand(0,156),mt_rand(0,156)); imagettftext($this->img,$this->fontsize,mt_rand(-30,30),$_x*$i+mt_rand(1,5),$this->height / 1.4,$this->fontcolor,$this->font,$this->code[$i]); } } private function createLine() { for ($i=0;$i<6;$i++) { $color = imagecolorallocate($this->img,mt_rand(0,156),mt_rand(0,156),mt_rand(0,156)); imageline($this->img,mt_rand(0,$this->width),mt_rand(0,$this->height),mt_rand(0,$this->width),mt_rand(0,$this->height),$color); } for ($i=0;$i<100;$i++) { $color = imagecolorallocate($this->img,mt_rand(200,255),mt_rand(200,255),mt_rand(200,255)); imagestring($this->img,mt_rand(1,5),mt_rand(0,$this->width),mt_rand(0,$this->height),'*',$color); } } private function outPut() { header('Content-type:image/png'); imagepng($this->img); imagedestroy($this->img); } public function doimg() { $this->createBg(); $this->createCode(); $this->createLine(); $this->createFont(); $this->outPut(); } public function getCode() { return strtolower($this->code); } } ?>
2.新建一个生成验证码的页面，此处取名为Code.php，然后引入上面的php代码，实例化类，调用上面的doimg方法。
<?php include("ValidateCode.php"); $obj = new ValidateCode(4); $obj->doimg(); ?>
3.上面的步骤做完后，就可以在其它页面通过img标签的src属性调用Code.php。
<html> <meta charset=utf8> <head><title>验证码</title></head> <body> <form action=""> 用户名：<input type="text" name="username"><br> 用户密码：<input type="password" name="userpwd"><br> 验证码：<input type="text" name="code"><img src="code.php" alt="yzm" onclick="this.src='code.php?id='+Math.random()" width="90px"> </form> </body> </html>
这样就完成了。