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//验证码
<?php //实现简单的验证码 //session_start session_start(); //画布 $image = imagecreatetruecolor(100, 30); //设置填充颜色 $bgcolor = imagecolorallocate($image, 255, 255, 255); //填充 imagefill($image, 0, 0, $bgcolor); //随机数据 //session $captcha_code = ‘‘; for ($i = 0; $i < 4; $i++) { $fontsize = 5; $fontcolor = imagecolorallocate($image, mt_rand(0, 120), mt_rand(0, 120), mt_rand(0, 120)); $data = ‘abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789‘; // echo strlen($data); // echo substr($data,61,1); $font = substr($data, mt_rand(0, strlen($data) - 1), 1); $captcha_code .= $font; $width = ($i * 100) / 4 + mt_rand(5, 10); $height = mt_rand(5, 10); //添加 imagestring($image, $fontsize, $width, $height, $font, $fontcolor); } //保存到session $_SESSION[‘authcode‘] = $captcha_code; //干扰 //像素点 for ($i = 0; $i < 200; $i++) { $pixcolor = imagecolorallocate($image, mt_rand(20, 200), mt_rand(20, 200), mt_rand(20, 200)); imagesetpixel($image, mt_rand(0, 99), mt_rand(0, 29), $pixcolor); } //线 for ($i = 0; $i < 4; $i++) { $linecolor = imagecolorallocate($image, mt_rand(50, 220), mt_rand(50, 220), mt_rand(50, 220)); imageline($image, mt_rand(0, 99), mt_rand(0, 29), mt_rand(0, 99), mt_rand(0, 99), $linecolor); } //输出 header(‘Content-type: image/png‘); imagepng($image); //销毁 imagedestroy($image);
//验证表单
<?php if (isset($_REQUEST[‘authcode‘])) { session_start(); //判断 if (strtolower($_REQUEST[‘authcode‘] == strtolower($_SESSION[‘authcode‘]))) { echo ‘恭喜你输入正确！‘; } else { echo ‘输入失败！‘; } exit(); } ?> <html> <head> <title>验证码提交</title> </head> <body> <form action="./form.php" method="post"> <p>验证码：<img src="./code01.php" id="captcha_img" alt="验证码" width="100" height="30" border="1px"></p> <a href="javascript:void(0)" onclick="document.getElementById(‘captcha_img‘).src=‘./code01.php?r=‘+Math.random()">看不清?</a> <p> <label for="authcode">请输入图片中的内容: </label> <input type="text" name="authcode" id="authcode"/> </p> <p><input type="submit" value="submit"/></p> </form> </body> </html>
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原文地址：http://www.cnblogs.com/tumio/p/4892980.html
