本文章给大家介绍一个非常不错的生成验证码的php程序，首先当用户请求http的时候，服务器端就创建一个唯一的sessionid，这个是session会话id，然后就去启动gd库或者imagemagick这些画图工具，把程序生成的随机的字符写到一张图片里面，然后显示到客户端,再由用户输入提交数据，然后我们程序把生成验证保存在session中进行比较，这样就完成了验证码的生成与验证了。
•新建一个php文件captcha_code_file.php代码如下复制代码//首先开启sessionsession_start();//定义前台显示验证码长&宽$image_width = 120;$image_height = 40;$characters_on_image = 6;$font = './monofont.ttf';//The characters that can be used in the CAPTCHA code.//avoid confusing characters (l 1 and i for example)$possible_letters = '23456789bcdfghjkmnpqrstvwxyz';$random_dots = 10;$random_lines = 30;$captcha_text_color="0x142864";$captcha_noice_color = "0x142864";//定义要生成验证码的字符串$code = '';$i = 0;while ($i$code .= substr($possible_letters, mt_rand(0, strlen($possible_letters)-1), 1);$i++;}$font_size = $image_height * 0.75;$image = @imagecreate($image_width, $image_height);/* setting the background, text and noise colours here */$background_color = imagecolorallocate($image, 255, 255, 255);$arr_text_color = hexrgb($captcha_text_color);$text_color = imagecolorallocate($image, $arr_text_color['red'],$arr_text_color['green'], $arr_text_color['blue']);$arr_noice_color = hexrgb($captcha_noice_color);$image_noise_color = imagecolorallocate($image, $arr_noice_color['red'],$arr_noice_color['green'], $arr_noice_color['blue']);/* generating the dots randomly in background */for( $i=0; $i imagefilledellipse($image, mt_rand(0,$image_width),mt_rand(0,$image_height), 2, 3, $image_noise_color);}/* generating lines randomly in background of image */for( $i=0; $i imageline($image, mt_rand(0,$image_width), mt_rand(0,$image_height),mt_rand(0,$image_width), mt_rand(0,$image_height), $image_noise_color);}/* create a text box and add 6 letters code in it */$textbox = imagettfbbox($font_size, 0, $font, $code);$x = ($image_width - $textbox[4])/2;$y = ($image_height - $textbox[5])/2;imagettftext($image, $font_size, 0, $x, $y, $text_color, $font , $code);/* Show captcha image in the page html page */header('Content-Type: image/jpeg');// defining the image type to be shown in browser widowimagejpeg($image);//showing the imageimagedestroy($image);//destroying the image instance//设置session，做验证$_SESSION['6_letters_code'] = $code;function hexrgb ($hexstr){$int = hexdec($hexstr);return array("red" => 0xFF & ($int >> 0x10),"green" => 0xFF & ($int >> 0x8),"blue" => 0xFF & $int);}调用页面显示验证码页面index.php PHP 8.5.5 PHP 8.5.5 是 PHP 8.5 分支的维护更新版本。该版本延续了“小步快跑”的迭代逻辑，通过深度错误修复、底层性能微调以及安全加固，旨在为开发者提供一个更健壮、更高效的运行环境。该版本严格遵守语义化版本规范，不包含破坏性变更。
下载代码如下复制代码session_start();if(isset($_REQUEST['Submit'])){// code for check server side validationif(empty($_SESSION['6_letters_code'] ) ||strcasecmp($_SESSION['6_letters_code'], $_POST['6_letters_code']) != 0){$msg="您输入的验证码有误，请重新输入!";}else{echo "您输入的是正确的!";// Captcha verification is Correct. Final Code Execute here!}}?>验证码Demo:@@##@@" id='captchaimg' onclick="refreshCaptcha();" >请输入验证码:如果看不到，请点我刷新一下!