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为什么完全按照老师写的代码验证吗出来会出现2层很多数字不是4位的

<?php

require_once 'string.func.php';

$width = 80;

$height = 28;

$image = imagecreatetruecolor($width, $height);

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

$black = imagecolorallocate($image, 0, 0, 0);

imagefilledrectangle($image, 1, 1, $width-2, $height-2, $white);

$type = 1;

$length = 4;

$chars = buildRandomString($type, $length);

$sess_name = "verify";

$_SESSION[$sess_name] = $chars;

$fontfiles = array(

"MSYH.TTF",

"MSYHBD.TTF",

"SIMFANG.TTF",

"SIMHEI.TTF",

"SIMKAI.TTF",

"SIMSUN.TTC"

);

for ($i = 0; $i < $length; $i ++) {

$size = mt_rand(14, 18);

$angle = mt_rand(- 15, 15);

$x = 5 + $i * $size;

$y = mt_rand(20, 26);

$fontfile = "../fonts/".$fontfiles[mt_rand(0,count($fontfiles)-1)];

$color = imagecolorallocate($image, mt_rand(50,90), mt_rand(80,200), mt_rand(90,180));

$text = substr($chars, $i, $length);

imagettftext($image, $size, $angle, $x, $y, $color, $fontfile, $text);

}

header("content-type:image/gif");

imagegif($image);

imagedestroy($image);

小龙upup

2017-04-17

源自：手把手教你实现电商网站后台开发 2-1

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小龙upup 提问者
2017-04-17

<?php
function buildRandomString($type=1,$length=4){
    if ($type == 1) {
        $chars = join("", range(0, 9));
    } elseif ($type == 2) {
        $chars = join("", array_merge(range('a', 'z'), range('A', 'Z')));
    } elseif ($type == 3) {
        $chars = join("", array_merge(range('a', 'z'), range('A', 'Z'), range(0, 9)));
    }
    if ($length > strlen($chars)) {
        exit("字符串长度不够");
    }
    $chars = str_shuffle($chars);
    return substr($chars, 0, $length);
}