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PHP implements login verification code verification function

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Release： 2023-03-29 06:14:01

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This article mainly introduces the verification code verification function in PHP in detail. It is mainly implemented by using the SESSION function in PHP. It has certain reference value. Interested friends can refer to it

The verification code is verified by using the SESSION function in PHP.

Declare the function at the top session_start(); 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(&#39;a&#39;,&#39;z&#39;),range(&#39;A&#39;,&#39;Z&#39;),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[&#39;session&#39;] = $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(&#39;content-type:image/png&#39;);//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($_POST[&#39;session&#39;])){
 session_start();
 if(strtolower($_POST[&#39;session&#39;])==strtolower($_SESSION[&#39;session&#39;])){
  echo&#39;<font color="#0000CC">输入正确</form>&#39;;
 }else{
  echo &#39;<font color="#CC0000"><b>输入错误</b></font>&#39;;
 }
 exit();
}

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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 id="img" border="1" src="http://localhost//xxx.php" width="100" height="30"></p>
 <a href="javascript:void(0)" rel="external nofollow"  onclick="document.getElementById(&#39;img&#39;).src=&#39;http://localhost//xxx.php&#39;">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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