PHP固定长度字符串

/**

 * 获取固定长度随机字符串

 * @param $n

 * @return string

 * @throws Exception

 */

function gf_rand_str($n) {

    if (!is_int($n)) {

        throw new Exception('argument must be int');

    }

    $alpha = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789';

    $str = '';

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

        $str .= $alpha[rand(0, 35)];

    }

    return $str;

}

前三位字母后三位数字：

function invite_num($len = 6)

{

    $en_chars = [

        "A", "B", "C", "D", "E", "F", "G",

        "H", "I", "J", "K", "L", "M", "N", "O", "P", "Q", "R",

        "S", "T", "U", "V", "W", "X", "Y", "Z"

    ];

    $num_chars = [

        "0", "1", "2", "3", "4", "5", "6", "7", "8", "9"

    ];

    $en_shuf = shuffle($en_chars);    // 将数组打乱

    $num_shuf = shuffle($num_chars);

    $output = "";

    for ($i = 0; $i < 3; $i++) {

        $output .= $en_chars[mt_rand(0, $len)];

    }

    $output .= substr(getMicroSecondsTimestamp(), 11, 1);

    $output .= rand(10, 99);

    return $output;

}

function getMicroSecondsTimestamp()

{

    $time = microtime();

    return substr($time, 11, 10) . str_pad(substr($time, 0, 8) * 1000000,

            6, "0", STR_PAD_LEFT);

}