PHP steps to implement verification code and server-side verification code

This article introduces to you the steps to implement verification code in PHP and the server-side verification code. It has certain reference value. Friends in need can refer to it. I hope it will be helpful to you.

What is the verification code: The verification code is a public program that distinguishes whether the user is a computer or a human.

It takes four steps to make a verification code

1: Generate a base map

2: Generate verification content

3: Generate verification code content

4: Verify verification content

First step by step, the first step, Generate base map:

Goal: Generate a 100*30 size image through php

Method: imagecreatetruecolor($width,$height);

Note Matters: Relying on GD extension

Before outputting a picture, the header information of that picture must be output in advance--》》Send native http header

This method outputs a black background by default

imagecreatetruecolor() Create a new true color image represented by $image. Later, it will be used a lot.

Since we are creating a true color image, we must have a variety of colors. Next, imagecolorallocate(select canvas, three colors Parameters)

What do you want to use to fill imagefill (select canvas, starting position, color)

With this, the base image is generated, let’s start adding some ingredients

$image = imagecreatetruecolor(100,30)

$bgcolor = imagecolorallocate($image,255,255,255);

imagefill($image,0,0,$bgcolor)

Step 2: Generate verification content

Goal: Randomly generate numbers (size, starting position, content, color)

Method: Generate a line of characters horizontally through loops and imagestring functions String (fill in according to the parameter position in imagestring)

Note: Control the font size, N/n

for($i=0;$<4;i){

Here, define variables based on the parameters in imagestring, and assign values ​​to variables

imagestring($image,$fontsze,$x,$y,$fontcontent,$fontcolor)

}

$fontcontent = substr($data,rand(0,strlen($data)),1);

If you want numbers and letters Combination, the substr method means to return the substring of the string. The returned string randomly obtains data. From here on, it has a length of up to 1

The third step is to generate the verification code content

Goal: Add interference elements to the verification code, interference elements are points or lines

Method: imagesetpixel point, imageline-line (resource file, starting position, color)

Notes: Interference elements Be sure to control the color and quantity to avoid overestimating the guest.

Step 4: Store the verification information through the session

Goal: Record on the server side to facilitate verification after the user enters the verification code

Method: session_start()

Note: session_start() must be at the top of the script

In the case of multiple services, centralized management of session management should be considered

imagepng Output the image to the browser or file in png format

imagedestroy Good habit of destroying the image

In these methods, a lot of resources are used, that is, each method requires the $image canvas

<php?
$image = imagecreatetruecolor( 100,30);
$bgcolor = imagecolorallocate($image,255,255,255);
imagefill($image,0,0,$bgcolor);
// for($i=0;$i<4;$i++){
// $fontsize = 6;
// $fontcolor = imagecolorallocate($image,rand(0,120),rand(0,120),rand(0,120));
// $fontcontent = rand(0,9);
// $x = ($i*100/4)+rand(5,10);
// $y = rand(5,10);
// imagestring($image,$fontsize,$x,$y,$fontcontent,$fontcolor );
// }
$captch_code= &#39;&#39;;
for($i=0 ;$i<4;$i++){
    $fontsize = 6;
    $fontcolor = imagecolorallocate($image,rand(0,120),rand(0,120),rand(0,120));
    $data = &#39;abcdefhijkimnpqrstuvwxy345678&#39;;
    $fontcontent = substr($data,rand(0,strlen($data)),1); 
    $captch_code.=$fontcontent;
    $x = ($i*100/4)+rand(5,10);
    $y = rand(5,10);
    imagestring($image,$fontsize,$x,$y,$fontcontent,$fontcolor );
    
}
$SESSION[&#39;authcode&#39;]=$captch_code;
for($i=0;$i<200;$i++){
$pointcolor = imagecolorallocate($image,rand(50,200),rand(50,200),rand(50,200));
imagesetpixel($image,rand(1,99),rand(1,99),$pointcolor);
}
for($i=0;$i<3;$i++){
$linecolor = imagecolorallocate($image,rand(80,220),rand(80,220),rand(80,220));
imageline($image,rand(1,99),rand(1,99),rand(1,99),rand(1,99),$pointcolor);
}
header(&#39;content-type: image/png&#39;);
imagepng( $image);
//end;
imagedestroy( $iamge);
?>

The production of verification code ends here. The next step is to perform verification on the server side

src="captcha-2.php?r=<?php echo rand();?>"   对于这个r 找了资料，没什么大用

This is the original intention

He also uses t here, so r ah t ah

Taking into account the case, strtolower() is used here to convert all uppercase letters entered by the user into lowercase letters

<?php

if(isset($_REQUEST[&#39;code&#39;]))
{
    session_start();
    if (strtolower($_REQUEST[&#39;code&#39;])==$_SESSION[&#39;code&#39;])
    {
        header(&#39;Content-type: text/html; charset=UTF8&#39;);
        echo &#39;<h1 color="#0000CC">输入正确</h1>&#39;;
    }
    else{
        header(&#39;Content-type: text/html; charset=UTF8&#39;);
        echo &#39;<h1 color="#CC0000"><b>输入错误</b></h1>&#39;;
    }
    exit();
}

?>
<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8"/>
    <title>确认验证</title>
</head>
<body>
<form method="post" action="form.php">
    <p>验证码图片：<img border="1" src="captcha-2.php?r=<?php echo rand();?>" width="100" height="30">

    </p>
    <p>请输入图片的内容：<input type="text" name="code" value=""/></p>
    <p><input type="submit" value="提交" style="padding:6px 20px;"></p>
</form>
</body>
</html>

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