php这是一个随机打印输出字符串的例子

<?php
header("Content-type:text/html;charset='utf8'");
error_reporting(E_ALL);

define("CAPTCHA_LEN", 16); // 随机数长度
$captchaSource = "0123456789abcdefghijklmnopqrstuvwxyz这是一个随机打印输出字符串的例子"; // 随机数字符源

$captchaResult = ""; // 随机数返回值
$captchaSentry = ""; // 随机数中间变量
for($i=0;$i<CAPTCHA_LEN;$i++){
    $n = rand(0, strlen($captchaSource));
    if($n >= 36){
        $n = 36 + ceil(($n - 36) / 3) * 3;
        $captchaResult .= substr($captchaSource, $n, 3);
    }else{
        $captchaResult .= substr($captchaSource, $n, 1);
    }
}

echo "随机打印输出字符串:".$captchaResult."<br>";