php - 列出字符类的成员

Question

我正在创建一个函数，我想从一组给定的字符中生成随机字符串。我想允许用户指定一个正则表达式字符类，而不是要求他们指定每个字符。
例如:

function a($length, $allowed_chars){
    for ($i = 0, $salt = ""; $i < $length; $i++){
        $salt .= __GET_ONE_RANDOM_CHAR_FROM_ALLOWED_CHARS__;
    }
}

如果 allowed chars 是所有允许字符的字符串，那么这很简单:

$characterList{mt_rand(0,strlen($characterList)-1)};

我希望能够像这样指定允许的字符 "./0-9A-Za-z" 而不是 "./0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"

Answer 1

怎么样:

// build a string with all printable char
$str = join('', range(' ','~'));
// define allowed char
$allowedChar = './a-zA-Z0-9';
// replace all non-allowed char by nothing, preg_quote escapes regex char
$str = preg_replace("~[^".preg_quote($allowedChar)."]~", "", $str);
echo $str,"\n";

输出:

./0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz