php显示随机验证码

<?php
header("Content-Type:image/png");
// $str="北京欢迎你!";
// imagefill($img,0,0,$color1);
// // imagestring($img,5,0,0,$str,$color2);

//1.产生随机字符串
$arr1 = array_merge(range('A','Z'),range(0,9),range('a','z'));
shuffle($arr1);
$arr2 = array_rand($arr1,4);
$str = "";
// print_r($arr2);
// echo "<br/>";
foreach($arr2 as $index){
    $str .= $arr1[$index];
}
// echo $str;
// 2.创建空画布
$width = 200;
$height = 100;

$img = imagecreatetruecolor($width,$height);
// 3.绘制带填充矩形
$color1 = imagecolorallocate($img,mt_rand(80,255),mt_rand(100,255),mt_rand(180,255));
$color2 = imagecolorallocate($img,255,0,0);
imagefilledrectangle($img,0,0,$width,$height,$color1);
// 4.绘制像素点
for ($i=0; $i <100; $i++) { 
    $color3=imagecolorallocate($img,mt_rand(0,255),mt_rand(0,255),mt_rand(0,255));    
    imagesetpixel($img,mt_rand(0,$width),mt_rand(0,$height),$color3);
}
$fontfile="F:\phpStudy\WWW\myweb\FZXBSJW.ttf";
imagettftext($img,24,0,60,60,$color2,$fontfile,$str);
imagepng($img);
imagedestroy($img);