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();
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
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'<font color="#0000CC">输入正确</form>';
}else{
echo '<font color="#CC0000"><b>输入错误</b></font>';
}
exit();
}The following is the HTML page code.
<!DOCTYPE html> <html> <head> <meta charset="utf-8"/> <title>确认验证码</title> </head> <body> <form method="post" action="./tushu.php"> <p>验证码图片:<img src="/static/imghwm/default1.png" data-src="http://localhost//xxx.php" class="lazy" id="img" border="1" style="max-width:90%" style="max-width:90%" alt="PHP implements login verification code function" ></p> <a href="javascript:void(0)" rel="external nofollow" onclick="document.getElementById('img').src='http://localhost//xxx.php'">看不清？换一个</a> <p>请输入图片中的验证码：<input type="text" name="session" value=""/></p> <p><input type="submit" value="提交" style="padding:6px 10px;"></p> </form> </body> </html>
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