PHP development verification code tutorial: adding content and disturbing elements

Let’s take a look at adding content and interference elements

<?php 
//创建一个画布
$width = 85;
$height = 30;
$type = 2;
$length = 4;
$line = 5;    //线的个数
$pix = 50; //点的个数
$img = imagecreatetruecolor($width, $height);

//准备填充的颜色
$white = imagecolorallocate($img,255,255,255);
$black = imagecolorallocate($img,0,0,0);

//向画布填充图形或者文字
imagefilledrectangle($img,1,1,$width-2,$height-2,$white);
$chars = rangeString($type,$length);
for($i=0;$i<$length;$i++){
    $size = mt_rand(14,18);
    $x = 5+$size*$i;
    $y = mt_rand(8,$length*2);
    $text = substr($chars,$i,1);
    $color = imagecolorallocate($img,mt_rand(50,90),mt_rand(90,200),mt_rand(80,120));
    imagestring($img,$size,$x,$y,$text,$color);
}
//障碍物像素点
for($i=0;$i<$pix;$i++){
  $px = mt_rand(1,$width-2);
  $py = mt_rand(1,$height-2);
  $color = imagecolorallocate($img,mt_rand(50,90),mt_rand(90,200),mt_rand(80,120));
  imagesetpixel($img, $px, $py, $color);
}
//障碍物横线
for($i=0;$i<$line;$i++){
    $color = imagecolorallocate($img,mt_rand(50,90),mt_rand(90,200),mt_rand(80,120));
    imageline($img,mt_rand(1,$width-2), mt_rand(1,$height-2),mt_rand(1,$width-2), mt_rand(1,$height-2),$color);
}


//输出图像
header("content-type:image/png");
imagepng($img);

//销毁资源
imagedestroy($img);

/**
 * 随机字符串
 * @param  [type] $type   int [1:数字;2:字母;3:数字加字母]
 * @param  [type] $length int 4
 * @return [type]         string
 */
function rangeString($type,$length){
    if($type==1){
       $chars = join("",range(0,9));
    }elseif($type==2){
       $chars = join("",array_merge(range("a","z"),range("A","Z")));
    }if($type==3){
        $chars = join("",array_merge(range(0,9),range("a","z"),range("A","Z")));
    }
    $chars = str_shuffle($chars);
    $chars = substr($chars,0,$length);
    return $chars;
}

With the above code, you can change the value of type $type=1 is a number

$type = 2 is an uppercase letter or lowercase Letters,

$type = 3 is a combination of numbers and letters,

you can try it