PHP implements login verification code function-PHP Tutorial-php.cn

This article mainly introduces how to write login verification code in PHP. Interested friends can refer to it. I hope it will be helpful to everyone.

Declare the function session_start(); at the top to tell the server that we want to use this function.

session_start();

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The next thing we use is the code to implement the verification code. Here we use English numeric codes as an example.

$image = imagecreatetruecolor(100, 30); //创建一个100×30的画布 $white = imagecolorallocate($image,255,255,255);//白色 imagefill($image,0,0,$white);//覆盖黑色画布

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Then declare an empty variable before the verification code is implemented to store the verification code.

$session = ""; //空变量 ，存放验证码 for($i=0;$i<4;$i++){ $size = 6; $x = $i*25+mt_rand(5,10); $y = mt_rand(5,10); $sizi_color = imagecolorallocate($image,mt_rand(80,220),mt_rand(80,220),mt_rand(80,220)); $char = join("",array_merge(range('a','z'),range('A','Z'),range(0,9))); $char = str_shuffle($char); $char = substr($char,0,1); imagestring($image,$size,$x,$y,$char,$sizi_color); $session .= $char ; //把验证码的每一个值赋值给变量 } $_SESSION['session'] = $session; //这个变量的值与用户输入的值相等

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for($k=0;$k<200;$k++){ $rand_color = imagecolorallocate($image,mt_rand(50,200),mt_rand(50,200),mt_rand(50,200)); imagesetpixel($image,mt_rand(1,99),mt_rand(1,29),$rand_color); } for($n=0;$n<5;$n++){ $line_color = imagecolorallocate($image,mt_rand(80,220),mt_rand(80,220),mt_rand(80,220)); imageline($image,mt_rand(1,99),mt_rand(1,29),mt_rand(1,99),mt_rand(1,29),$line_color); } header('content-type:image/png');//设置文件输出格式 imagepng( $image ); //以png格式输出$image图像 imagedestroy( $image ); //销毁图像

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Use POST method to receive verification code. The strtolower function makes the server case-insensitive. This can effectively reduce the user's input error rate.

if(isset($_POST['session'])){ session_start(); if(strtolower($_POST['session'])==strtolower($_SESSION['session'])){ echo'输入正确'; }else{ echo '输入错误'; } exit(); }

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The following is the HTML page code.

    确认验证码 
   验证码图片:
 看不清？换一个 请输入图片中的验证码：

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