PHP uses the GD library to implement a simple verification code

$img=imagecreatetruecolor(100, 40);
$red=imagecolorallocate($img, 255, 0, 0);
$green=imagecolorallocate($img, 0, 255, 0) ;
$blue=imagecolorallocate($img, 0, 0, 255);
$white=imagecolorallocate($img, 255, 255, 255);
$black=imagecolorallocate($img, 0, 0, 0);
 //Generate image
imagefill($img, 0, 0, $black);
//Set verification code
$code="";
for($i=0;$i<5;$i++){
$ code.=rand(0,9);
}
//Write the verification code into the image
imagestring($img, 5, 20, 15, $code, $white);
//Add a little interference
for($ i=0;$i<10;$i++){
imagesetpixel($img, rand(0,100), rand(0,40), $red);
imagesetpixel($img, rand(0,100), rand(0, 40), $green);
imagesetpixel($img, rand(0,100), rand(0,40), $blue);
}
//Add some interference
for($i=0;$i<1 ;$i++){
imageline($img, rand(0,50), rand(0,20), rand(50,100), rand(20,40), $red);
imageline($img, rand(0 ,50), rand(0,20), rand(50,100), rand(20,40), $green);
imageline($img, rand(0,50), rand(0,20), rand(50,100 ), rand(20,40), $blue);
}
header("Content-type:image/png");
imagepng($img);
imagedestroy($img);
?>

Verification code, PHP