(PHP 7, PHP 8)
random_bytes — Get cryptographically secure random bytes
$length): stringGenerates a string containing uniformly selected random bytes with the requested length.
As the returned bytes are selected completely randomly, the resulting string is likely to contain unprintable characters or invalid UTF-8 sequences. It may be necessary to encode it before transmission or display.
The randomness generated by this function is suitable for all applications, including the generation of long-term secrets, such as encryption keys.
此函数使用的随机性来源先后顺序如下：
Linux：» getrandom()、/dev/urandom
FreeBSD >= 12（PHP >= 7.3）：» getrandom()、/dev/urandom
Windows（PHP >= 7.2）：» CNG-API
Windows：» CryptGenRandom
macOS（PHP >= 8.2；>= 8.1.9；>= 8.0.22 如果 CCRandomGenerateBytes 在编译时可用）：CCRandomGenerateBytes()
macOS（PHP >= 8.1；>= 8.0.2）：arc4random_buf()、/dev/urandom
NetBSD >= 7（PHP >= 7.1；>= 7.0.1）：arc4random_buf()、/dev/urandom
OpenBSD >= 5.5（PHP >= 7.1；>= 7.0.1）：arc4random_buf()、/dev/urandom
DragonflyBSD（PHP >= 8.1）：» getrandom()、/dev/urandom
Solaris（PHP >= 8.1）：» getrandom()、/dev/urandom
注意: 虽然此函数是 PHP 7.0 添加到 PHP 中，但是从 PHP 5.2 到 PHP 5.6 都可以用 » 用户级实现。
length
The length of the random string that should be returned in bytes; must be 1 or greater.
A string containing the requested number of cryptographically secure random bytes.
length is less than 1,
a ValueError will be thrown.
| 版本 | 说明 |
|---|---|
| 8.2.0 | In case of a CSPRNG failure, this function will now throw a Random\RandomException. Previously a plain Exception was thrown. |
示例 #1 random_bytes() example
<?php
$bytes = random_bytes(5);
var_dump(bin2hex($bytes));
?>以上示例的输出类似于：
string(10) "385e33f741"
<?php
function str_rand(int $length = 64){ // 64 = 32
$length = ($length < 4) ? 4 : $length;
return bin2hex(random_bytes(($length-($length%2))/2));
}
var_dump(str_rand());
// d6199909d0b5fdc22c9db625e4edf0d6da2b113b21878cde19e96f4afe69e714
?>