PHP verification code generation principle and implementation

Verification codes are implemented more and more in forms, but verification codes written in js always feel inconvenient, so I learned verification codes implemented in php. Well, I actually had nothing to do, but I didn’t want to waste time, so I learned how to implement verification codes in PHP. As the saying goes, having too many skills does not weigh you down. Moreover, it can also be encapsulated into a function, which is very convenient for future use. Of course, it is not encapsulated now.

First of all, here is a rendering:

Since registration codes are often used when registering to prevent machines from maliciously registering, here I will post a basic image that generates a png image verification code. It is very simple but thoughtful. Very clear:

1. Generate a png picture
2. Set the background color for the picture
3. Set the font color and style
4. Generate a 4-digit random verification code
5. Put each character generated Adjust the rotation angle and position and draw it on the png image
6. Add noise and interference lines to prevent registration machines from analyzing the original image for malicious registration
7. Output the image
8. Release the memory occupied by the image

authcode.php file

code

<&#63;php
session_start ();
header ( 'Content-type: image/png' );
//创建图片
$im = imagecreate($x=130,$y=45 );
$bg = imagecolorallocate($im,rand(50,200),rand(0,155),rand(0,155)); //第一次对 imagecolorallocate() 的调用会给基于调色板的图像填充背景色
$fontColor = imageColorAllocate ( $im, 255, 255, 255 ); //字体颜色
$fontstyle = 'rock.ttf'; //字体样式，这个可以从c:\windows\Fonts\文件夹下找到，我把它放到和authcode.php文件同一个目录，这里可以替换其他的字体样式
//产生随机字符
for($i = 0; $i < 4; $i ++) {
$randAsciiNumArray = array (rand(48,57),rand(65,90));
$randAsciiNum = $randAsciiNumArray [rand ( 0, 1 )];
$randStr = chr ( $randAsciiNum );
imagettftext($im,30,rand(0,20)-rand(0,25),5+$i*30,rand(30,35),$fontColor,$fontstyle,$randStr);
$authcode .= $randStr; 
}
$_SESSION['authcode'] = $randFourStr;//用户和用户输入的验证码做比较
//干扰线
for ($i=0;$i<8;$i++){
$lineColor = imagecolorallocate($im,rand(0,255),rand(0,255),rand(0,255));
imageline ($im,rand(0,$x),0,rand(0,$x),$y,$lineColor);
}
//干扰点
for ($i=0;$i<250;$i++){
imagesetpixel($im,rand(0,$x),rand(0,$y),$fontColor);
}
imagepng($im);
imagedestroy($im); 
&#63;>

The above is the relevant knowledge about the principle and implementation of PHP verification code generation. I hope it will be helpful to everyone.

The above introduces the principle and implementation of PHP verification code generation, including various aspects. I hope it will be helpful to friends who are interested in PHP tutorials.